Fabrication of three dimensional objects with variable slice thickness

ABSTRACT

A method of forming the body portion of a three-dimensional object from a polymerizable liquid by the process of continuous liquid interface printing is described. The process includes advancing a carrier for the object away from a build surface while irradiating a build region between the carrier and build surface in a pattern of advancing and irradiating defined by an operating mode, with the body portion having a plurality of contiguous segments and with the irradiating carried out in sequentially presented slices of exposure, each having a pattern that corresponds to a segment of the body portion. Each segment has a thickness (e.g., in Z or vertical dimension) during the forming thereof. In the present invention, slice thickness is changed among the slices at least once during the formation of the body portion.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 62/128,686, filed Mar. 5, 2015, the disclosure ofwhich is incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The present invention concerns methods and apparatus for the fabricationof solid three-dimensional objects from liquid materials.

BACKGROUND OF THE INVENTION

In conventional additive or three-dimensional fabrication techniques,construction of a three-dimensional object is performed in a step-wiseor layer-by-layer manner. In particular, layer formation is performedthrough solidification of photo curable resin under the action ofvisible or UV light irradiation. Two techniques are known: one in whichnew layers are formed at the top surface of the growing object; theother in which new layers are formed at the bottom surface of thegrowing object.

If new layers are formed at the top surface of the growing object, thenafter each irradiation step the object under construction is loweredinto the resin “pool,” a new layer of resin is coated on top, and a newirradiation step takes place. An early example of such a technique isgiven in Hull, U.S. Pat. No. 5,236,637, at FIG. 3. A disadvantage ofsuch “top down” techniques is the need to submerge the growing object ina (potentially deep) pool of liquid resin and reconstitute a preciseoverlayer of liquid resin.

If new layers are formed at the bottom of the growing object, then aftereach irradiation step the object under construction must be separatedfrom the bottom plate in the fabrication well. An early example of sucha technique is given in Hull, U.S. Pat. No. 5,236,637, at FIG. 4. Whilesuch “bottom up” techniques hold the potential to eliminate the need fora deep well in which the object is submerged by instead lifting theobject out of a relatively shallow well or pool, a problem with such“bottom up” fabrication techniques, as commercially implemented, is thatextreme care must be taken, and additional mechanical elements employed,when separating the solidified layer from the bottom plate due tophysical and chemical interactions therebetween. For example, in U.S.Pat. No. 7,438,846, an elastic separation layer is used to achieve“non-destructive” separation of solidified material at the bottomconstruction plane. Other approaches, such as the B9Creator™3-dimensional printer marketed by B9Creations of Deadwood, S. Dak., USA,employ a sliding build plate. See, e.g., M. Joyce, US Patent App.2013/0292862 and Y. Chen et al., US Patent App. 2013/0295212 (both Nov.7, 2013); see also Y. Pan et al., J. Manufacturing Sci. and Eng. 134,051011-1 (October 2012). Such approaches introduce a mechanical stepthat may complicate the apparatus, slow the method, and/or potentiallydistort the end product.

Continuous processes for producing a three-dimensional object aresuggested at some length with respect to “top down” techniques in U.S.Pat. No. 7,892,474, but this reference does not explain how they may beimplemented in “bottom up” systems in a manner non-destructive to thearticle being produced. Accordingly, there is a need for alternatemethods and apparatus for three-dimensional fabrication that can obviatethe need for mechanical separation steps in “bottom-up” fabrication.

SUMMARY OF THE INVENTION

Described herein are methods, systems and apparatus (includingassociated control methods, systems and apparatus), for the productionof a three-dimensional object by additive manufacturing. In preferred(but not necessarily limiting) embodiments, the method is carried outcontinuously. In preferred (but not necessarily limiting) embodiments,the three-dimensional object is produced from a liquid interface. Hencethey are sometimes referred to, for convenience and not for purposes oflimitation, as “continuous liquid interphase printing” or “continuousliquid interface production” (“CLIP”) herein (the two being usedinterchangeably). See, e.g., J. Tumbleston et al., Continuous liquidinterface production of 3D objects, Science 347, 1349-1352 (publishedonline Mar. 16, 2015). A schematic representation of one embodimentthereof is given in FIG. 1 herein.

The present invention provides a method of forming a three-dimensionalobject, comprising:

providing a carrier and an optically transparent member having a buildsurface, said carrier and said build surface defining a build regiontherebetween;

filling said build region with a polymerizable liquid,

continuously or intermittently irradiating said build region with lightthrough said optically transparent member to form a solid polymer fromsaid polymerizable liquid, and

continuously or intermittently advancing (e.g., sequentially orconcurrently with said irradiating step) said carrier away from saidbuild surface to form said three-dimensional object from said solidpolymer.

In some embodiments, illumination is carried out sequentially, andpreferably at higher intensity (e.g., in “strobe” mode), as describedfurther below.

In some embodiments, fabrication is carried out in two or threesequential patterns, from a base zone, through an optional transitionzone, to a body zone, as described further below.

In some embodiments, the carrier is vertically reciprocated with respectto the build surface to enhance or speed the refilling of the buildregion with the polymerizable liquid.

In some embodiments, operating mode and/or slice thickness is changed atleast once in the course of fabricating the three dimensional object.

In some preferred embodiments of CLIP, the filling, irradiating, and/oradvancing steps are carried out while also concurrently: (i)continuously maintaining a dead zone (or persistent liquid interface) ofpolymerizable liquid in contact with said build surface, and (ii)continuously maintaining a gradient of polymerization zone (which, asdiscussed below, may also be described as an active surface on thebottom of the growing three dimensional object) between said dead zoneand said solid polymer and in contact with each thereof, said gradientof polymerization zone comprising said polymerizable liquid in partiallycured form. Stated differently, in some preferred embodiments of CLIP,the three dimensional object, or at least some contiguous portionthereof, is formed or produced in situ. “In situ” as used herein has itsmeaning in the field of chemical engineering, and means “in place.” Forexample, where both the growing portion of the three-dimensional objectand the build surface (typically with their intervening active surfaceor gradient of polymerization, and dead zone) are maintained in placeduring formation of at least a portion of the 3D object, or sufficientlyin place to avoid the formation of fault lines or planes in the 3Dobject. For example, in some embodiments according to the invention,different portions of the 3D object, which are contiguous with oneanother in the final 3D object, can both be formed sequentially from orwithin a gradient of polymerization or active surface. Furthermore, afirst portion of the 3D object can remain in the gradient ofpolymerization or contacting the active surface while a second portion,that is contiguous with the first portion, is formed in the gradient ofpolymerization. Accordingly, the 3D object can be remotely fabricated,grown or produced continuously from the gradient of polymerization oractive surface (rather than fabricated in discrete layers). The deadzone and gradient of polymerization zone/active surface may bemaintained through some or all of the formation of the object beingmade, for example (and in some embodiments) for a time of at least 5,10, 20, or 30 seconds, and in some embodiments for a time of at least 1or 2 minutes.

Apparatus for carrying out the present invention generally comprises:

(a) a support;

(b) a carrier operatively associated with said support on which carriersaid three-dimensional object is formed;

(c) an optically transparent member having a build surface, with saidbuild surface and said carrier defining a build region therebetween;

(d) a liquid polymer supply operatively associated with said buildsurface and configured to supply liquid polymer into said build regionfor solidification or polymerization;

(e) a radiation source configured to irradiate said build region throughsaid optically transparent member to form a solid polymer from saidpolymerizable liquid;

(f) optionally at least one drive operatively associated with eithersaid transparent member or said carrier;

(g) a controller operatively associated with said carrier, and/oroptionally said at least one drive, and said radiation source foradvancing said carrier away from said build surface to form saidthree-dimensional object from said solid polymer,

with the controller preferably further configured to oscillate orreciprocate said carrier with respect to said build surface to enhanceor speed the refilling of said build region with said polymerizableliquid.

In the B9Creator™ 3-dimensional printer, a polydimethylsiloxane (PDMS)coating is applied to the sliding build surface. The PDMS coating issaid to absorb oxygen and create a thin lubricating film ofunpolymerized resin through its action as a polymerization inhibitor.However, the PDMS coated build surface is directly replenished withoxygen by mechanically moving (sliding) the surface from beneath thegrowing object, while wiping unpolymerized resin therefrom with a wiperblade, and then returning it to its previous position beneath thegrowing object. While in some embodiments auxiliary means of providingan inhibitor such as oxygen are provided (e.g., a compressor toassociated channels), the process still employs a layer-by-layerapproach with sliding and wiping of the surface. Since the PDMS coatingmay be swollen by the resin, this swelling, along with these mechanicalsteps, may result in tearing of or damage to the PDMS coating.

In some embodiments, the polymerizable liquid comprises a mixture of (i)a light polymerizable liquid first component, and (ii) a secondsolidifiable component that is different from the first component. Inthis case, the method may further include, concurrently with orfollowing the forming of the three dimensional object, solidifyingand/or curing the second solidifiable component in the three-dimensionalobject (e.g., by removing the three-dimensional object as an“intermediate” object from the carrier, and heating and/or microwaveirradiating the object).

In some embodiments, the second component comprises a polymerizableliquid solubilized in or suspended in the first component.

In some embodiments, the second component comprises: (i) a polymerizablesolid suspended in the first component; (ii) a polymerizable solidsolubilized in the first component; or (iii) a polymer solubilized inthe first component.

In some embodiments, the three-dimensional intermediate is collapsibleor compressible.

In some embodiments, the three-dimensional object, following the furthersolidifying and/or curing, comprises a polymer blend, interpenetratingpolymer network, semi-interpenetrating polymer network, or sequentialinterpenetrating polymer network formed from the first component and thesecond component.

In some embodiments, the polymerizable liquid comprises: from 1 or 10percent by weight to 40, 90 or 99 percent by weight of the firstcomponent; and from 1, 10 or 60 percent by weight to 90 or 99 percent byweight of the second component.

In some embodiments, the further solidifying and/or curing step (d) iscarried out concurrently with the irradiating step (c) and: (i) thesolidifying and/or curing step is carried out by precipitation; or (ii)the irradiating step generates heat from the polymerization of the firstcomponent in an amount sufficient to thermally solidify or polymerizethe second component.

In some embodiments, the further solidifying and/or curing step iscarried out subsequent to the irradiating step (c) and is carried outby: (i) heating the second solidifiable component; (ii) irradiating thesecond solidifiable component with light at a wavelength different fromthat of the light in the irradiating step (c); (iii) contacting thesecond polymerizable component to water; and/or (iv) contacting thesecond polymerizable component to a catalyst.

In some embodiments, the second component comprises the precursors to apolyurethane, polyurea, or copolymer thereof, a silicone resin, an epoxyresin, a cyanate ester resin, or a natural rubber; and the solidifyingstep is carried out by heating and/or microwave irradiating.

In some embodiments, the second component comprises the precursors to apolyurethane, polyurea, or copolymer thereof, and the solidifying and/orcuring step is carried out by contacting the second component to water.

In some embodiments, the further solidifying and/or curing step iscarried out subsequent to the irradiating step; and the solidifyingand/or curing step is carried out under conditions in which the solidpolymer scaffold degrades and forms a constituent necessary for thepolymerization of the second component.

In some embodiments, the second component comprises precursors to apolyurethane, polyurea, or copolymer thereof, a silicone resin, aring-opening metathesis polymerization resin, or a click chemistryresin, a cyanate ester resin, and the solidifying and/or curing step iscarried out by contacting the second component to a polymerizationcatalyst.

In some embodiments, the polymerizable liquid comprises a firstcomponent (Part A) and at least one additional component (Part B), thefirst component comprising monomers and/or prepolymers that can bepolymerized by exposure to actinic radiation or light; the secondcomponent solidifiable on contacting to heat, water, water vapor, lightat a different wavelength than that at which the first component ispolymerized, catalysts, evaporation of a solvent from the polymerizableliquid, exposure to microwave irradiation, and combinations thereof.

In some embodiments employing two-component polymerizable liquids, thethree-dimensional object comprises an interpenetrating polymer network(IPN), the interpenetrating polymer network comprising a sol-gelcomposition, a hydrophobic-hydrophilic IPN, a phenolic resin, apolyimide, a conductive polymer, a natural product-based IPN, asequential IPN, a polyolefin, or a combination thereof.

Non-limiting examples and specific embodiments of the present inventionare explained in greater detail in the drawings herein and thespecification set forth below. The disclosure of all United StatesPatent references cited herein are to be incorporated herein byreference in their entirety.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of one embodiment of a method of thepresent invention.

FIG. 2 is a perspective view of one embodiment of an apparatus of thepresent invention.

FIG. 3 is a first flow chart illustrating control systems and methodsfor carrying out the present invention.

FIG. 4 is a second flow chart illustrating control systems and methodsfor carrying out the present invention.

FIG. 5 is a third flow chart illustrating control systems and methodsfor carrying out the present invention.

FIG. 6 is a graphic illustration of a process of the inventionindicating the position of the carrier in relation to the build surfaceor plate, where both advancing of the carrier and irradiation of thebuild region is carried out continuously. Advancing of the carrier isillustrated on the vertical axis, and time is illustrated on thehorizontal axis.

FIG. 7 is a graphic illustration of another process of the inventionindicating the position of the carrier in relation to the build surfaceor plate, where both advancing of the carrier and irradiation of thebuild region is carried out stepwise, yet the dead zone and gradient ofpolymerization are maintained. Advancing of the carrier is againillustrated on the vertical axis, and time is illustrated on thehorizontal axis.

FIG. 8 is a graphic illustration of still another process of theinvention indicating the position of the carrier in relation to thebuild surface or plate, where both advancing of the carrier andirradiation of the build region is carried out stepwise, the dead zoneand gradient of polymerization are maintained, and a reciprocating stepis introduced between irradiation steps to enhance the flow ofpolymerizable liquid into the build region. Advancing of the carrier isagain illustrated on the vertical axis, and time is illustrated on thehorizontal axis.

FIG. 9 is a detailed illustration of a reciprocation step of FIG. 8,showing a period of acceleration occurring during the upstroke (i.e., agradual start of the upstroke) and a period of deceleration occurringduring the downstroke (i.e., a gradual end to the downstroke).

FIG. 10 schematically illustrates the movement of the carrier (z) overtime (t) in the course of fabricating a three-dimensional object byprocesses of the present invention through a first base (or “adhesion”)zone, a second transition zone, and a third body zone.

FIG. 11A schematically illustrates the movement of the carrier (z) overtime (t) in the course of fabricating a three-dimensional object bycontinuous advancing and continuous exposure.

FIG. 11B illustrates the fabrication of a three-dimensional object in amanner similar to FIG. 11A, except that illumination is now in anintermittent (or “strobe”) pattern.

FIG. 12A schematically illustrates the movement of the carrier (z) overtime (t) in the course of fabricating a three-dimensional object byintermittent (or “stepped”) advancing and intermittent exposure.

FIG. 12B illustrates the fabrication of a three-dimensional object in amanner similar to FIG. 12A, except that illumination is now in ashortened intermittent (or “strobe”) pattern.

FIG. 13A schematically illustrates the movement of the carrier (z) overtime (t) in the course of fabricating a three-dimensional object byoscillatory advancing and intermittent exposure.

FIG. 13B illustrates the fabrication of a three-dimensional object in amanner similar to FIG. 13A, except that illumination is now in ashortened intermittent (or “strobe”) pattern.

FIG. 14A schematically illustrates one segment of a “strobe” pattern offabrication, where the duration of the static portion of the carrier hasbeen shortened to near the duration of the “strobe” exposure

FIG. 14B is a schematic illustration of a segment of a strobe pattern offabrication similar to FIG. 14A, except that the carrier is now movingslowly upward during the period of strobe illumination.

FIG. 15A is a schematic illustration of the fabrication of athree-dimensional object similar to FIG. 13A, except that the bodysegment is fabricated in two contiguous segments, with the first segmentcarried out in an oscillatory operating mode, and the second segmentcarried out in a continuous operating mode.

FIG. 15B is a schematic illustration of the fabrication of athree-dimensional object similar to FIG. 15A, except that oscillatoryoperating modes are replaced with stepped operating modes.

FIG. 16A is a schematic illustration of the fabrication of athree-dimensional object similar to FIG. 11A, except that the bodysegment is fabricated in three contiguous segments, with the first andthird segments carried out in a continuous operating mode, and thesecond segment carried out in oscillatory operating mode.

FIG. 16B is a schematic illustration of the fabrication of athree-dimensional object similar to FIG. 16A, except that theoscillatory operating mode is replaced with a stepped operating mode.

FIG. 17A is a schematic illustration of the fabrication of athree-dimensional object similar to FIG. 16A, except that the base zone,transition zone, and first segment of the body zone are carried out in astrobe continuous operating mode, the second segment of the body zone isfabricated in an oscillatory operating mode, and the third segment ofthe body zone is fabricated in a continuous operating mode.

FIG. 17B is similar to FIG. 17A, except that the second segment of thebody zone is fabricated in a stepped operating mode.

FIG. 18A is a schematic illustration of the fabrication of athree-dimensional object similar to FIG. 11A, except that lightintensity is varied in the course of fabricating the base and transitionzones, and both light intensity and rate of advancing are varied in thecourse of fabricating the body zone.

FIG. 18B is a schematic illustration of the fabrication of athree-dimensional object similar to FIG. 17A, except that light isinterrupted in an intermittent fashion (dashed line representing lightintensity during interrupted segments is for comparison to FIG. 17Aonly).

FIG. 19 is a schematic illustration of the fabrication of athree-dimensional object similar to FIG. 11A, except that the mode ofoperation during fabrication of the body segment is changed multipletimes for continuous, to reciprocal, and back.

FIG. 20 schematically illustrates parameters that may be varied within areciprocal or step-wise operating mode.

FIG. 21A schematically illustrates a method of the invention carried outin a continuous operating mode, with constant slice thickness andconstant carrier speed.

FIG. 21B schematically illustrates a method of the invention carried outin a continuous operating mode, with variable slice thickness withconstant carrier speed.

FIG. 21C schematically illustrates a method of the invention carried outin a continuous operating mode, with constant slice thickness andvariable carrier speed.

FIG. 21D schematically illustrates a method of the invention carried outin continuous operating mode, mode with variable slice thickness andvariable carrier speed.

FIG. 21E schematically illustrates a method of the invention carried outin reciprocal operating mode, with constant slice thickness.

FIG. 21F schematically illustrates a method of the invention carried outin reciprocal operating mode, with variable slice thickness.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present invention is now described more fully hereinafter withreference to the accompanying drawings, in which embodiments of theinvention are shown. This invention may, however, be embodied in manydifferent forms and should not be construed as limited to theembodiments set forth herein; rather these embodiments are provided sothat this disclosure will be thorough and complete and will fully conveythe scope of the invention to those skilled in the art.

Like numbers refer to like elements throughout. In the figures, thethickness of certain lines, layers, components, elements or features maybe exaggerated for clarity. Where used, broken lines illustrate optionalfeatures or operations unless specified otherwise.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a,” “an” and “the” are intended toinclude plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises” or“comprising,” when used in this specification, specify the presence ofstated features, integers, steps, operations, elements components and/orgroups or combinations thereof, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,elements, components and/or groups or combinations thereof.

As used herein, the term “and/or” includes any and all possiblecombinations or one or more of the associated listed items, as well asthe lack of combinations when interpreted in the alternative (“or”).

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the specification andclaims and should not be interpreted in an idealized or overly formalsense unless expressly so defined herein. Well-known functions orconstructions may not be described in detail for brevity and/or clarity.

It will be understood that when an element is referred to as being “on,”“attached” to, “connected” to, “coupled” with, “contacting,” etc.,another element, it can be directly on, attached to, connected to,coupled with and/or contacting the other element or intervening elementscan also be present. In contrast, when an element is referred to asbeing, for example, “directly on,” “directly attached” to, “directlyconnected” to, “directly coupled” with or “directly contacting” anotherelement, there are no intervening elements present. It will also beappreciated by those of skill in the art that references to a structureor feature that is disposed “adjacent” another feature can have portionsthat overlap or underlie the adjacent feature.

Spatially relative terms, such as “under,” “below,” “lower,” “over,”“upper” and the like, may be used herein for ease of description todescribe an element's or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is inverted, elements described as “under” or “beneath” otherelements or features would then be oriented “over” the other elements orfeatures. Thus the exemplary term “under” can encompass both anorientation of over and under. The device may otherwise be oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly. Similarly, the terms“upwardly,” “downwardly,” “vertical,” “horizontal” and the like are usedherein for the purpose of explanation only, unless specificallyindicated otherwise.

It will be understood that, although the terms first, second, etc., maybe used herein to describe various elements, components, regions, layersand/or sections, these elements, components, regions, layers and/orsections should not be limited by these terms. Rather, these terms areonly used to distinguish one element, component, region, layer and/orsection, from another element, component, region, layer and/or section.Thus, a first element, component, region, layer or section discussedherein could be termed a second element, component, region, layer orsection without departing from the teachings of the present invention.The sequence of operations (or steps) is not limited to the orderpresented in the claims or figures unless specifically indicatedotherwise.

1. Polymerizable liquids/part A components.

Any suitable polymerizable liquid can be used to enable the presentinvention. In some embodiments, the polymerizable liquid comprises, inaddition to a first component (or “part A”) such as described in thissection, a second component (or “part B”) such as described in the “DualHardening” section below. The liquid (sometimes also referred to as“liquid resin” “ink,” or simply “resin” herein) can include a monomer,particularly photopolymerizable and/or free radical polymerizablemonomers, and a suitable initiator such as a free radical initiator, andcombinations thereof. Examples include, but are not limited to,acrylics, methacrylics, acrylamides, styrenics, olefins, halogenatedolefins, cyclic alkenes, maleic anhydride, alkenes, alkynes, carbonmonoxide, functionalized oligomers, multifunctional cure site monomers,functionalized PEGs, etc., including combinations thereof. Examples ofliquid resins, monomers and initiators include but are not limited tothose set forth in U.S. Pat. Nos. 8,232,043; 8,119,214; 7,935,476;7,767,728; 7,649,029; WO 2012129968 A1; CN 102715751 A; JP 2012210408 A.

Acid catalyzed polymerizable liquids. While in some embodiments as notedabove the polymerizable liquid comprises a free radical polymerizableliquid (in which case an inhibitor may be oxygen as described below), inother embodiments the polymerizable liquid comprises an acid catalyzed,or cationically polymerized, polymerizable liquid. In such embodimentsthe polymerizable liquid comprises monomers contain groups suitable foracid catalysis, such as epoxide groups, vinyl ether groups, etc. Thussuitable monomers include olefins such as methoxyethene,4-methoxystyrene, styrene, 2-methylprop-1-ene, 1,3-butadiene, etc.;heterocycloic monomers (including lactones, lactams, and cyclic amines)such as oxirane, thietane, tetrahydrofuran, oxazoline, 1,3, dioxepane,oxetan-2-one, etc., and combinations thereof. A suitable (generallyionic or non-ionic) photoacid generator (PAG) is included in the acidcatalyzed polymerizable liquid, examples of which include, but are notlimited to onium salts, sulfonium and iodonium salts, etc., such asdiphenyl iodide hexafluorophosphate, diphenyl iodide hexafluoroarsenate,diphenyl iodide hexafluoroantimonate, diphenyl p-methoxyphenyl triflate,diphenyl p-toluenyl triflate, diphenyl p-isobutylphenyl triflate,diphenyl p-tert-butylphenyl triflate, triphenylsulfoniumhexafluororphosphate, triphenylsulfonium hexafluoroarsenate,triphenylsulfonium hexafluoroantimonate, triphenylsulfonium triflate,dibutylnaphthylsulfonium triflate, etc., including mixtures thereof.See, e.g., U.S. Pat. Nos. 7,824,839; 7,550,246; 7,534,844; 6,692,891;5,374,500; and 5,017,461; see also Photoacid Generator Selection Guidefor the electronics industry and energy curable coatings (BASF 2010).

Hydrogels. In some embodiments suitable resins includes photocurablehydrogels like poly(ethylene glycols) (PEG) and gelatins. PEG hydrogelshave been used to deliver a variety of biologicals, including Growthfactors; however, a great challenge facing PEG hydrogels crosslinked bychain growth polymerizations is the potential for irreversible proteindamage. Conditions to maximize release of the biologicals fromphotopolymerized PEG diacrylate hydrogels can be enhanced by inclusionof affinity binding peptide sequences in the monomer resin solutions,prior to photopolymerization allowing sustained delivery. Gelatin is abiopolymer frequently used in food, cosmetic, pharmaceutical andphotographic industries. It is obtained by thermal denaturation orchemical and physical degradation of collagen.

There are three kinds of gelatin, including those found in animals, fishand humans Gelatin from the skin of cold water fish is considered safeto use in pharmaceutical applications. UV or visible light can be usedto crosslink appropriately modified gelatin. Methods for crosslinkinggelatin include cure derivatives from dyes such as Rose Bengal.Photocurable silicone resins. A suitable resin includes photocurablesilicones. UV cure silicone rubber, such as Silopren™ UV Cure SiliconeRubber can be used as can LOCTITE™ Cure Silicone adhesives sealants.Applications include optical instruments, medical and surgicalequipment, exterior lighting and enclosures, electricalconnectors/sensors, fiber optics and gaskets.

Biodegradable resins. Biodegradable resins are particularly importantfor implantable devices to deliver drugs or for temporary performanceapplications, like biodegradable screws and stents (U.S. Pat. Nos.7,919,162; 6,932,930). Biodegradable copolymers of lactic acid andglycolic acid (PLGA) can be dissolved in PEG dimethacrylate to yield atransparent resin suitable for use. Polycaprolactone and PLGA oligomerscan be functionalized with acrylic or methacrylic groups to allow themto be effective resins for use.

Photocurable polyurethanes. A particularly useful resin is photocurablepolyurethanes. A photopolymerizable polyurethane composition comprising(1) a polyurethane based on an aliphatic diisocyanate,poly(hexamethylene isophthalate glycol) and, optionally, 1,4-butanediol;(2) a polyfunctional acrylic ester; (3) a photoinitiator; and (4) ananti-oxidant, can be formulated so that it provides a hard,abrasion-resistant, and stain-resistant material (U.S. Pat. No.4,337,130). Photocurable thermoplastic polyurethane elastomersincorporate photoreactive diacetylene diols as chain extenders.

High performance resins. In some embodiments, high performance resinsare used. Such high performance resins may sometimes require the use ofheating to melt and/or reduce the viscosity thereof, as noted above anddiscussed further below. Examples of such resins include, but are notlimited to, resins for those materials sometimes referred to as liquidcrystalline polymers of esters, ester-imide, and ester-amide oligomers,as described in U.S. Pat. Nos. 7,507,784; 6,939,940. Since such resinsare sometimes employed as high-temperature thermoset resins, in thepresent invention they further comprise a suitable photoinitiator suchas benzophenone, anthraquinone, and fluoroenone initiators (includingderivatives thereof), to initiate cross-linking on irradiation, asdiscussed further below.

Additional example resins. Particularly useful resins for dentalapplications include EnvisionTEC's Clear Guide, EnvisionTEC's E-DenstoneMaterial. Particularly useful resins for hearing aid industries includeEnvisionTEC's e-Shell 300 Series of resins. Particularly useful resinsinclude EnvisionTEC's HTM140IV High Temperature Mold Material for usedirectly with vulcanized rubber in molding/casting applications. Aparticularly useful material for making tough and stiff parts includesEnvisionTEC's RC31 resin. A particulary useful resin for investmentcasting applications includes EnvisionTEC's Easy Cast EC500.

Additional resin ingredients. The liquid resin or polymerizable materialcan have solid particles suspended or dispersed therein. Any suitablesolid particle can be used, depending upon the end product beingfabricated. The particles can be metallic, organic/polymeric, inorganic,or composites or mixtures thereof. The particles can be nonconductive,semi-conductive, or conductive (including metallic and non-metallic orpolymer conductors); and the particles can be magnetic, ferromagnetic,paramagnetic, or nonmagnetic. The particles can be of any suitableshape, including spherical, elliptical, cylindrical, etc. The particlescan comprise an active agent or detectable compound as described below,though these may also be provided dissolved solubilized in the liquidresin as also discussed below. For example, magnetic or paramagneticparticles or nanoparticles can be employed. The resin or polymerizablematerial may contain a dispersing agent, such as an ionic surfactant, anon-ionic surfactant, a block copolymer, or the like.

The liquid resin can have additional ingredients solubilized therein,including pigments, dyes, active compounds or pharmaceutical compounds,detectable compounds (e.g., fluorescent, phosphorescent, radioactive),etc., again depending upon the particular purpose of the product beingfabricated. Examples of such additional ingredients include, but are notlimited to, proteins, peptides, nucleic acids (DNA, RNA) such as siRNA,sugars, small organic compounds (drugs and drug-like compounds), etc.,including combinations thereof.

Inhibitors of polymerization. Inhibitors or polymerization inhibitorsfor use in the present invention may be in the form of a liquid or agas. In some embodiments, gas inhibitors are preferred. The specificinhibitor will depend upon the monomer being polymerized and thepolymerization reaction. For free radical polymerization monomers, theinhibitor can conveniently be oxygen, which can be provided in the formof a gas such as air, a gas enriched in oxygen (optionally but in someembodiments preferably containing additional inert gases to reducecombustibility thereof), or in some embodiments pure oxygen gas. Inalternate embodiments, such as where the monomer is polymerized byphotoacid generator initiator, the inhibitor can be a base such asammonia, trace amines (e.g. methyl amine, ethyl amine, di and trialkylamines such as dimethyl amine, diethyl amine, trimethyl amine, triethylamine, etc.), or carbon dioxide, including mixtures or combinationsthereof

Polymerizable liquids carrying live cells. In some embodiments, thepolymerizable liquid may carry live cells as “particles” therein. Suchpolymerizable liquids are generally aqueous, and may be oxygenated, andmay be considered as “emulsions” where the live cells are the discretephase. Suitable live cells may be plant cells (e.g., monocot, dicot),animal cells (e.g., mammalian, avian, amphibian, reptile cells),microbial cells (e.g., prokaryote, eukaryote, protozoal, etc.), etc. Thecells may be of differentiated cells from or corresponding to any typeof tissue (e.g., blood, cartilage, bone, muscle, endocrine gland,exocrine gland, epithelial, endothelial, etc.), or may beundifferentiated cells such as stem cells or progenitor cells. In suchembodiments the polymerizable liquid can be one that forms a hydrogel,including but not limited to those described in U.S. Pat. Nos.7,651,683; 7,651,682; 7,556,490; 6,602,975; 5,836,313; etc.

2. Apparatus.

A non-limiting embodiment of an apparatus of the invention is shown inFIG. 2. It comprises a radiation source 11 such as a digital lightprocessor (DLP) providing electromagnetic radiation 12 which thoughreflective mirror 13 illuminates a build chamber defined by wall 14 anda rigid build plate 15 forming the bottom of the build chamber, whichbuild chamber is filled with liquid resin 16. The bottom of the chamber15 is constructed of build plate comprising a semipermeable member asdiscussed further below. The top of the object under construction 17 isattached to a carrier 18. The carrier is driven in the verticaldirection by linear stage 19, although alternate structures can be usedas discussed below.

A liquid resin reservoir, tubing, pumps liquid level sensors and/orvalves can be included to replenish the pool of liquid resin in thebuild chamber (not shown for clarity) though in some embodiments asimple gravity feed may be employed. Drives/actuators for the carrier orlinear stage, along with associated wiring, can be included inaccordance with known techniques (again not shown for clarity). Thedrives/actuators, radiation source, and in some embodiments pumps andliquid level sensors can all be operatively associated with a suitablecontroller, again in accordance with known techniques.

Build plates 15 used to carry out the present invention generallycomprise or consist of a (typically rigid or solid, stationary, and/orfixed) semipermeable (or gas permeable) member, alone or in combinationwith one or more additional supporting substrates (e.g., clamps andtensioning members to rigidify an otherwise flexible semipermeablematerial). The semipermeable member can be made of any suitable materialthat is optically transparent at the relevant wavelengths (or otherwisetransparent to the radiation source, whether or not it is visuallytransparent as perceived by the human eye—i. e., an opticallytransparent window may in some embodiments be visually opaque),including but not limited to porous or microporous glass, and the rigidgas permeable polymers used for the manufacture of rigid gas permeablecontact lenses. See, e.g., Norman G. Gaylord, U.S. Pat. No. RE31,406;see also U.S. Pat. Nos. 7,862,176; 7,344,731; 7,097,302; 5,349,394;5,310,571; 5,162,469; 5,141,665; 5,070,170; 4,923,906; and 4,845,089. Insome embodiments such materials are characterized as glassy and/oramorphous polymers and/or substantially crosslinked that they areessentially non-swellable. Preferably the semipermeable member is formedof a material that does not swell when contacted to the liquid resin ormaterial to be polymerized (i.e., is “non-swellable”). Suitablematerials for the semipermeable member include amorphous fluoropolymers,such as those described in U.S. Pat. Nos. 5,308,685 and 5,051,115. Forexample, such fluoropolymers are particularly useful over silicones thatwould potentially swell when used in conjunction with organic liquidresin inks to be polymerized. For some liquid resin inks, such as moreaqueous-based monomeric systems and/or some polymeric resin ink systemsthat have low swelling tendencies, silicone based window materials maybesuitable. The solubility or permeability of organic liquid resin inkscan be dramatically decreased by a number of known parameters includingincreasing the crosslink density of the window material or increasingthe molecular weight of the liquid resin ink. In some embodiments thebuild plate may be formed from a thin film or sheet of material which isflexible when separated from the apparatus of the invention, but whichis clamped and tensioned when installed in the apparatus (e.g., with atensioning ring) so that it is rendered fixed or rigid in the apparatus.Particular materials include TEFLON AF® fluoropolymers, commerciallyavailable from DuPont. Additional materials include perfluoropolyetherpolymers such as described in U.S. Pat. Nos. 8,268,446; 8,263,129;8,158,728; and 7,435,495.

It will be appreciated that essentially all solid materials, and most ofthose described above, have some inherent “flex” even though they may beconsidered “rigid,” depending on factors such as the shape and thicknessthereof and environmental factors such as the pressure and temperatureto which they are subjected. In addition, the Willis “stationary” or“fixed” with respect to the build plate is intended to mean that nomechanical interruption of the process occurs, or no mechanism orstructure for mechanical interruption of the process (as in alayer-by-layer method or apparatus) is provided, even if a mechanism forincremental adjustment of the build plate (for example, adjustment thatdoes not lead to or cause collapse of the gradient of polymerizationzone) is provided), or if the build surface contributes to reciprocationto aid feeding of the polymerizable liquid, as described further below.

The semipermeable member typically comprises a top surface portion, abottom surface portion, and an edge surface portion. The build surfaceis on the top surface portion; and the feed surface may be on one, two,or all three of the top surface portion, the bottom surface portion,and/or the edge surface portion. In the embodiment illustrated in FIG. 2the feed surface is on the bottom surface portion, but alternateconfigurations where the feed surface is provided on an edge, and/or onthe top surface portion (close to but separate or spaced away from thebuild surface) can be implemented with routine skill.

The semipermeable member has, in some embodiments, a thickness of from0.01, 0.1 or 1 millimeters to 10 or 100 millimeters, or more (dependingupon the size of the item being fabricated, whether or not it islaminated to or in contact with an additional supporting plate such asglass, etc., as discussed further below.

The permeability of the semipermeable member to the polymerizationinhibitor will depend upon conditions such as the pressure of theatmosphere and/or inhibitor, the choice of inhibitor, the rate or speedof fabrication, etc. In general, when the inhibitor is oxygen, thepermeability of the semipermeable member to oxygen may be from 10 or 20Barrers, up to 1000 or 2000 Barrers, or more. For example, asemipermeable member with a permeability of 10 Barrers used with a pureoxygen, or highly enriched oxygen, atmosphere under a pressure of 150PSI may perform substantially the same as a semipermeable member with apermeability of 500 Barrers when the oxygen is supplied from the ambientatmosphere under atmospheric conditions.

Thus, the semipermeable member may comprise a flexible polymer film(having any suitable thickness, e.g., from 0.001, 0.01, 0.05, 0.1 or 1millimeters to 1, 5, 10, or 100 millimeters, or more), and the buildplate may further comprise a tensioning member (e.g., a peripheral clampand an operatively associated strain member or stretching member, as ina “drum head”; a plurality of peripheral clamps, etc., includingcombinations thereof) connected to the polymer film and to fix andrigidify the film (e.g., at least sufficiently so that the film does notstick to the object as the object is advanced and resiliently orelastically rebound therefrom). The film has a top surface and a bottomsurface, with the build surface on the top surface and the feed surfacepreferably on the bottom surface. In other embodiments, thesemipermeable member comprises: (i) a polymer film layer (having anysuitable thickness, e.g., from 0.001, 0.01, 0.1 or 1 millimeters to 5,10 or 100 millimeters, or more), having a top surface positioned forcontacting said polymerizable liquid and a bottom surface, and (ii) arigid, gas permeable, optically transparent supporting member (havingany suitable thickness, e.g., from 0.01, 0.1 or 1 millimeters to 10,100, or 200 millimeters, or more), contacting said film layer bottomsurface. The supporting member has a top surface contacting the filmlayer bottom surface, and the supporting member has a bottom surfacewhich may serve as the feed surface for the polymerization inhibitor.Any suitable materials that are semipermeable (that is, permeable to thepolymerization inhibitor) may be used. For example, the polymer film orpolymer film layer may, for example, be a fluoropolymer film, such as anamorphous thermoplastic fluoropolymer like TEFLON AF 1600™ or TEFLON AF2400™ fluoropolymer films, or perfluoropolyether (PFPE), particularly acrosslinked PFPE film, or a crosslinked silicone polymer film. Thesupporting member comprises a silicone or crosslinked silicone polymermember such as a polydimethylxiloxane member, a rigid gas permeablepolymer member, or a porous or microporous glass member. Films can belaminated or clamped directly to the rigid supporting member withoutadhesive (e.g., using PFPE and PDMS materials), or silane couplingagents that react with the upper surface of a PDMS layer can be utilizedto adhere to the first polymer film layer. UV-curable,acrylate-functional silicones can also be used as a tie layer betweenUV-curable PFPEs and rigid PDMS supporting layers.

When configured for placement in the apparatus, the carrier defines a“build region” on the build surface, within the total area of the buildsurface. Because lateral “throw” (e.g., in the X and/or Y directions) isnot required in the present invention to break adhesion betweensuccessive layers, as in the Joyce and Chen devices noted previously,the area of the build region within the build surface may be maximized(or conversely, the area of the build surface not devoted to the buildregion may be minimized). Hence in some embodiments, the total surfacearea of the build region can occupy at least fifty, sixty, seventy,eighty, or ninety percent of the total surface area of the buildsurface.

As shown in FIG. 2, the various components are mounted on a support orframe assembly 20. While the particular design of the support or frameassembly is not critical and can assume numerous configurations, in theillustrated embodiment it is comprised of a base 21 to which theradiation source 11 is securely or rigidly attached, a vertical member22 to which the linear stage is operatively associated, and a horizontaltable 23 to which wall 14 is removably or securely attached (or on whichthe wall is placed), and with the build plate rigidly fixed, eitherpermanently or removably, to form the build chamber as described above.

As noted above, the build plate can consist of a single unitary andintegral piece of a rigid semipermeable member, or can compriseadditional materials. For example, a porous or microporous glass can belaminated or fixed to a rigid semipermeable material. Or, asemipermeable member as an upper portion can be fixed to a transparentlower member having purging channels formed therein for feeding gascarrying the polymerization inhibitor to the semipermeable member(through which it passes to the build surface to facilitate theformation of a release layer of unpolymerized liquid material, as notedabove and below). Such purge channels may extend fully or partiallythrough the base plate: For example, the purge channels may extendpartially into the base plate, but then end in the region directlyunderlying the build surface to avoid introduction of distortion.Specific geometries will depend upon whether the feed surface for theinhibitor into the semipermeable member is located on the same side oropposite side as the build surface, on an edge portion thereof, or acombination of several thereof.

Any suitable radiation source (or combination of sources) can be used,depending upon the particular resin employed, including electron beamand ionizing radiation sources. In a preferred embodiment the radiationsource is an actinic radiation source, such as one or more lightsources, and in particular one or more ultraviolet light sources. Anysuitable light source can be used, such as incandescent lights,fluorescent lights, phosphorescent or luminescent lights, a laser,light-emitting diode, etc., including arrays thereof. The light sourcepreferably includes a pattern-forming element operatively associatedwith a controller, as noted above. In some embodiments, the light sourceor pattern forming element comprises a digital (or deformable)micromirror device (DMD) with digital light processing (DLP), a spatialmodulator (SLM), or a microelectromechanical system (MEMS) mirror array,a mask (aka a reticle), a silhouette, or a combination thereof. See,U.S. Pat. No. 7,902,526. Preferably the light source comprises a spatiallight modulation array such as a liquid crystal light valve array ormicromirror array or DMD (e.g., with an operatively associated digitallight processor, typically in turn under the control of a suitablecontroller), configured to carry out exposure or irradiation of thepolymerizable liquid without a mask, e.g., by maskless photolithography.See, e.g., U.S. Pat. Nos. 6,312,134; 6,248,509; 6,238,852; and5,691,541.

In some embodiments, as discussed further below, there may be movementin the X and/or Y directions concurrently with movement in the Zdirection, with the movement in the X and/or Y direction hence occurringduring polymerization of the polymerizable liquid (this is in contrastto the movement described in Y. Chen et al., or M. Joyce, supra, whichis movement between prior and subsequent polymerization steps for thepurpose of replenishing polymerizable liquid). In the present inventionsuch movement may be carried out for purposes such as reducing “burn in”or fouling in a particular zone of the build surface.

Because an advantage of some embodiments of the present invention isthat the size of the build surface on the semipermeable member (i.e.,the build plate or window) may be reduced due to the absence of arequirement for extensive lateral “throw” as in the Joyce or Chendevices noted above, in the methods, systems and apparatus of thepresent invention lateral movement (including movement in the X and/or Ydirection or combination thereof) of the carrier and object (if suchlateral movement is present) is preferably not more than, or less than,80, 70, 60, 50, 40, 30, 20, or even 10 percent of the width (in thedirection of that lateral movement) of the build region.

While in some embodiments the carrier is mounted on an elevator toadvance up and away from a stationary build plate, on other embodimentsthe converse arrangement may be used: That is, the carrier may be fixedand the build plate lowered to thereby advance the carrier awaytherefrom. Numerous different mechanical configurations will be apparentto those skilled in the art to achieve the same result.

Depending on the choice of material from which the carrier isfabricated, and the choice of polymer or resin from which the article ismade, adhesion of the article to the carrier may sometimes beinsufficient to retain the article on the carrier through to completionof the finished article or “build.” For example, an aluminum carrier mayhave lower adhesion than a poly(vinyl chloride) (or “PVC”) carrier.Hence one solution is to employ a carrier comprising a PVC on thesurface to which the article being fabricated is polymerized. If thispromotes too great an adhesion to conveniently separate the finishedpart from the carrier, then any of a variety of techniques can be usedto further secure the article to a less adhesive carrier, including butnot limited to the application of adhesive tape such as “Greener MaskingTape for Basic Painting #2025 High adhesion” to further secure thearticle to the carrier during fabrication.

3. Controller and Process Control.

The methods and apparatus of the invention can include process steps andapparatus features to implement process control, including feedback andfeed-forward control, to, for example, enhance the speed and/orreliability of the method.

A controller for use in carrying out the present invention may beimplemented as hardware circuitry, software, or a combination thereof Inone embodiment, the controller is a general purpose computer that runssoftware, operatively associated with monitors, drives, pumps, and othercomponents through suitable interface hardware and/or software. Suitablesoftware for the control of a three-dimensional printing or fabricationmethod and apparatus as described herein includes, but is not limitedto, the ReplicatorG open source 3d printing program, 3DPrint™ controllersoftware from 3D systems, Slic3r, Skeinforge, KISSlicer, Repetier-Host,PrintRun, Cura, etc., including combinations thereof.

Process parameters to directly or indirectly monitor, continuously orintermittently, during the process(e.g., during one, some or all of saidfilling, irradiating and advancing steps) include, but are not limitedto, irradiation intensity, temperature of carrier, polymerizable liquidin the build zone, temperature of growing product, temperature of buildplate, pressure, speed of advance, pressure, force (e.g., exerted on thebuild plate through the carrier and product being fabricated), strain(e.g., exerted on the carrier by the growing product being fabricated),thickness of release layer, etc.

Known parameters that may be used in feedback and/or feed-forwardcontrol systems include, but are not limited to, expected consumption ofpolymerizable liquid (e.g., from the known geometry or volume of thearticle being fabricated), degradation temperature of the polymer beingformed from the polymerizable liquid, etc.

Process conditions to directly or indirectly control, continuously orstep-wise, in response to a monitored parameter, and/or known parameters(e.g., during any or all of the process steps noted above), include, butare not limited to, rate of supply of polymerizable liquid, temperature,pressure, rate or speed of advance of carrier, intensity of irradiation,duration of irradiation (e.g. for each “slice”), etc.

For example, the temperature of the polymerizable liquid in the buildzone, or the temperature of the build plate, can be monitored, directlyor indirectly with an appropriate thermocouple, non-contact temperaturesensor (e.g., an infrared temperature sensor), or other suitabletemperature sensor, to determine whether the temperature exceeds thedegradation temperature of the polymerized product. If so, a processparameter may be adjusted through a controller to reduce the temperaturein the build zone and/or of the build plate. Suitable process parametersfor such adjustment may include: decreasing temperature with a cooler,decreasing the rate of advance of the carrier, decreasing intensity ofthe irradiation, decreasing duration of radiation exposure, etc.

In addition, the intensity of the irradiation source (e.g., anultraviolet light source such as a mercury lamp) may be monitored with aphotodetector to detect a decrease of intensity from the irriadiationsource (e.g., through routine degredation thereof during use). Ifdetected, a process parameter may be adjusted through a controller toaccommodate the loss of intensity. Suitable process parameters for suchadjustment may include: increasing temperature with a heater, decreasingthe rate of advance of the carrier, increasing power to the lightsource, etc.

As another example, control of temperature and/or pressure to enhancefabrication time may be achieved with heaters and coolers (individually,or in combination with one another and separately responsive to acontroller), and/or with a pressure supply (e.g., pump, pressure vessel,valves and combinations thereof) and/or a pressure release mechanismsuch as a controllable valve (individually, or in combination with oneanother and separately responsive to a controller).

In some embodiments the controller is configured to maintain thegradient of polymerization zone described herein (see, e.g., FIG. 1)throughout the fabrication of some or all of the final product. Thespecific configuration (e.g., times, rate or speed of advancing,radiation intensity, temperature, etc.) will depend upon factors such asthe nature of the specific polymerizable liquid and the product beingcreated. Configuration to maintain the gradient of polymerization zonemay be carried out empirically, by entering a set of process parametersor instructions previously determined, or determined through a series oftest runs or “trial and error”; configuration may be provided throughpre-deter mined instructions; configuration may be achieved by suitablemonitoring and feedback (as discussed above), combinations thereof, orin any other suitable manner

In some embodiments, a method and apparatus as described above may becontrolled by a software program running in a general purpose computerwith suitable interface hardware between that computer and the apparatusdescribed above. Numerous alternatives are commercially available.Non-limiting examples of one combination of components is shown in FIGS.3 to 5, where “Microcontroller” is Parallax Propeller, the Stepper MotorDriver is Sparkfun EasyDriver, the LED Driver is a Luxeon Single LEDDriver, the USB to Serial is a Parallax USB to Serial converter, and theDLP System is a Texas Instruments LightCrafter system.

4. General Methods.

As noted above, the present invention provides a method of forming athree-dimensional object, comprising the steps of: (a) providing acarrier and a build plate, said build plate comprising a semipermeablemember, said semipermeable member comprising a build surface and a feedsurface separate from said build surface, with said build surface andsaid carrier defining a build region therebetween, and with said feedsurface in fluid contact with a polymerization inhibitor; then(concurrently and/or sequentially) (b) filing said build region with apolymerizable liquid, said polymerizable liquid contacting said buildsegment, (c) irradiating said build region through said build plate toproduce a solid polymerized region in said build region, with a liquidfilm release layer comprised of said polymerizable liquid formed betweensaid solid polymerized region and said build surface, the polymerizationof which liquid film is inhibited by said polymerization inhibitor; and(d) advancing said carrier with said polymerized region adhered theretoaway from said build surface on said stationary build plate to create asubsequent build region between said polymerized region and said topzone. In general the method includes (e) continuing and/or repeatingsteps (b) through (d) to produce a subsequent polymerized region adheredto a previous polymerized region until the continued or repeateddeposition of polymerized regions adhered to one another forms saidthree-dimensional object.

Since no mechanical release of a release layer is required, or nomechanical movement of a build surface to replenish oxygen is required,the method can be carried out in a continuous fashion, though it will beappreciated that the individual steps noted above may be carried outsequentially, concurrently, or a combination thereof Indeed, the rate ofsteps can be varied over time depending upon factors such as the densityand/or complexity of the region under fabrication.

Also, since mechanical release from a window or from a release layergenerally requires that the carrier be advanced a greater distance fromthe build plate than desired for the next irradiation step, whichenables the window to be recoated, and then return of the carrier backcloser to the build plate (e.g., a “two steps forward one step back”operation), the present invention in some embodiments permitselimination of this “back-up” step and allows the carrier to be advancedunidirectionally, or in a single direction, without intervening movementof the window for re-coating, or “snapping” of a pre-formed elasticrelease-layer. However, in other embodiments of the invention,reciprocation is utilized not for the purpose of obtaining release, butfor the purpose of more rapidly filling or pumping polymerizable liquidinto the build region.

In some embodiments, the advancing step is carried out sequentially inuniform increments (e.g., of from 0.1 or 1 microns, up to 10 or 100microns, or more) for each step or increment. In some embodiments, theadvancing step is carried out sequentially in variable increments (e.g.,each increment ranging from 0.1 or 1 microns, up to 10 or 100 microns,or more) for each step or increment. The size of the increment, alongwith the rate of advancing, will depend in part upon factors such astemperature, pressure, structure of the article being produced (e.g.,size, density, complexity, configuration, etc.)

In other embodiments of the invention, the advancing step is carried outcontinuously, at a uniform or variable rate.

In some embodiments, the rate of advance (whether carried outsequentially or continuously) is from about 0.1 1, or 10 microns persecond, up to about to 100, 1,000, or 10,000 microns per second, againdepending again depending on factors such as temperature, pressure,structure of the article being produced, intensity of radiation, etc

As described further below, in some embodiments the filling step iscarried out by forcing said polymerizable liquid into said build regionunder pressure. In such a case, the advancing step or steps may becarried out at a rate or cumulative or average rate of at least 0.1, 1,10, 50, 100, 500 or 1000 microns per second, or more. In general, thepressure may be whatever is sufficient to increase the rate of saidadvancing step(s) at least 2, 4, 6, 8 or 10 times as compared to themaximum rate of repetition of said advancing steps in the absence ofsaid pressure. Where the pressure is provided by enclosing an apparatussuch as described above in a pressure vessel and carrying the processout in a pressurized atmosphere (e.g., of air, air enriched with oxygen,a blend of gasses, pure oxygen, etc.) a pressure of 10, 20, 30 or 40pounds per square inch (PSI) up to, 200, 300, 400 or 500 PSI or more,may be used. For fabrication of large irregular objects higher pressuresmay be less preferred as compared to slower fabrication times due to thecost of a large high pressure vessel. In such an embodiment, both thefeed surface and the polymerizable liquid can be in fluid contact withthe same compressed gas (e.g., one comprising from 20 to 95 percent byvolume of oxygen, the oxygen serving as the polymerization inhibitor.

On the other hand, when smaller items are fabricated, or a rod or fiberis fabricated that can be removed or exited from the pressure vessel asit is produced through a port or orifice therein, then the size of thepressure vessel can be kept smaller relative to the size of the productbeing fabricated and higher pressures can (if desired) be more readilyutilized.

As noted above, the irradiating step is in some embodiments carried outwith patterned irradiation. The patterned irradiation may be a fixedpattern or may be a variable pattern created by a pattern generator(e.g., a DLP) as discussed above, depending upon the particular itembeing fabricated.

When the patterned irradiation is a variable pattern rather than apattern that is held constant over time, then each irradiating step maybe any suitable time or duration depending on factors such as theintensity of the irradiation, the presence or absence of dyes in thepolymerizable material, the rate of growth, etc. Thus in someembodiments each irradiating step can be from 0.001, 0.01, 0.1, 1 or 10microseconds, up to 1, 10, or 100 minutes, or more, in duration. Theinterval between each irradiating step is in some embodiments preferablyas brief as possible, e.g., from 0.001, 0.01, 0.1, or 1 microseconds upto 0.1, 1, or 10 seconds.

While the dead zone and the gradient of polymerization zone do not havea strict boundary therebetween (in those locations where the two meet),the thickness of the gradient of polymerization zone is in someembodiments at least as great as the thickness of the dead zone. Thus,in some embodiments, the dead zone has a thickness of from 0.01, 0.1, 1,2, or 10 microns up to 100, 200 or 400 microns, or more, and/or saidgradient of polymerization zone and said dead zone together have athickness of from 1 or 2 microns up to 400, 600, or 1000 microns, ormore. Thus the gradient of polymerization zone may be thick or thindepending on the particular process conditions at that time. Where thegradient of polymerization zone is thin, it may also be described as anactive surface on the bottom of the growing three-dimensional object,with which monomers can react and continue to form growing polymerchains therewith. In some embodiments, the gradient of polymerizationzone, or active surface, is maintained (while polymerizing stepscontinue) for a time of at least 5, 10, 15, 20 or 30 seconds, up to 5,10, 15 or 20 minutes or more, or until completion of thethree-dimensional product.

The method may further comprise the step of disrupting said gradient ofpolymerization zone/active surface, for a time sufficient to form acleavage line in said three-dimensional object (e.g., at a predetermineddesired location for intentional cleavage, or at a location in saidobject where prevention of cleavage or reduction of cleavage isnon-critical), and then reinstating said gradient of polymerization zone(e.g. by pausing, and resuming, the advancing step, increasing, thendecreasing, the intensity of irradiation, and combinations thereof

In some embodiments the build surface is flat; in other the buildsurface is irregular such as convexly or concavely curved, or has wallsor trenches formed therein. In either case the build surface may besmooth or textured.

Curved and/or irregular build plates or build surfaces can be used infiber or rod formation, to provide different materials to a singleobject being fabricated (that is, different polymerizable liquids to thesame build surface through channels or trenches formed in the buildsurface, each associated with a separate liquid supply, etc.

Carrier Feed Channels for Polymerizable liquid. While polymerizableliquid may be provided directly to the build plate from a liquid conduitand reservoir system, in some embodiments the carrier include one ormore feed channels therein. The carrier feed channels are in fluidcommunication with the polymerizable liquid supply, for example areservoir and associated pump. Different carrier feed channels may be influid communication with the same supply and operate simultaneously withone another, or different carrier feed channels may be separatelycontrollable from one another (for example, through the provision of apump and/or valve for each). Separately controllable feed channels maybe in fluid communication with a reservoir containing the samepolymerizable liquid, or may be in fluid communication with a reservoircontaining different polymerizable liquids. Through the use of valveassemblies, different polymerizable liquids may in some embodiments bealternately fed through the same feed channel, if desired.

5. Reciprocating Feed of Polymerizable Liquid.

In an embodiment of the present invention, the carrier is verticallyreciprocated (or oscillated) with respect to the build surface (that is,the two are vertically reciprocated with respect to one another) toenhance or speed the refilling of the build region with thepolymerizable liquid. Such reciprocations or oscillations (these twoterms being used interchangeably herein) may be of any suitableconfiguration, including uniform and non-uniform, and/or periodic ornon-periodic, with respect to one another, so long as they areconfigured to enhance feed of the polymerizable liquid to the buildsurface.

In some embodiments, the vertically reciprocating step, which comprisesan upstroke and a downstroke, is carried out with the distance of travelof the upstroke being greater than the distance of travel of thedownstroke, to thereby concurrently carry out the advancing step (thatis, driving the carrier away from the build plate in the Z dimension) inpart or in whole.

In some embodiments, the speed of the upstroke gradually accelerates(that is, there is provided a gradual start and/or gradual accelerationof the upstroke, over a period of at least 20, 30, 40, or 50 percent ofthe total time of the upstroke, until the conclusion of the upstroke, orthe change of direction which represents the beginning of thedownstroke. Stated differently, the upstroke begins, or starts, gentlyor gradually.

In some embodiments, the speed of the downstroke gradually decelerates(that is, there is provided a gradual termination and/or gradualdeceleration of the downstroke, over a period of at least 20, 30, 40, or50 percent of the total time of the downstroke. Stated differently, thedownstroke concludes, or ends, gently or gradually.

While in some embodiments there is an abrupt end, or abruptdeceleration, of the upstroke, and an abrupt beginning or accelerationof the downstroke (e.g., a rapid change in vector or direction of travelfrom upstroke to downstroke), it will be appreciated that gradualtransitions may be introduced here as well (e.g., through introductionof a “plateau” or pause in travel between the upstroke and downstroke).It will also be appreciated that, while each reciprocating step may beconsist of a single upstroke and downstroke, the reciprocation step maycomprise a plurality of 2, 3, 4 or 5 or more linked set ofreciprocations, which may e the same or different in frequent and/oramplitude

In some embodiments, the vertically reciprocating step is carried outover a total time of from 0.01 or 0.1 seconds up to 1 or 10 seconds(e.g., per cycle of an upstroke and a downstroke).

In some embodiments, the upstroke distance of travel is from 0.02 or 0.2millimeters (or 20 or 200 microns) to 1 or 10 millimeters (or 1000 to10,000 microns). The distance of travel of the downstroke may be thesame as, or less than, the distance of travel of the upstroke, where alesser distance of travel for the downstroke serves to achieve theadvancing of the carrier away from the build surface as thethree-dimensional object is gradually formed. Where a reciprocation stepcomprises multiple linked reciprocations, the sum distance of travel ofall upstrokes in that set is preferably greater than the sum distance oftravel of all downstrokes in that set, to achieve the advancing of thecarrier away from the build surface as the three-dimensional object isgradually formed.

Preferably the vertically reciprocating step, and particularly theupstroke thereof, does not cause the formation of gas bubbles or a gaspocket in the build region, but instead the build region remains filledwith the polymerizable liquid throughout the reciprocation steps, andthe gradient of polymerization zone or region remains in contact withthe “dead zone” and with the growing object being fabricated throughoutthe reciprocation steps. As will be appreciated, a purpose of thereciprocation is to speed or enhance the refilling of the build region,particularly where larger build regions are to be refilled withpolymerizable liquid, as compared to the speed at which the build regioncould be refilled without the reciprocation step.

In some embodiments, the advancing step is carried out intermittently ata rate of 1, 2, 5 or 10 individual advances per minute up to 300, 600,or 1000 individual advances per minute, each followed by a pause duringwhich an irradiating step is carried out. It will be appreciated thatone or more reciprocation steps (e.g., upstroke plus downstroke) may becarried out within each advancing step. Stated differently, thereciprocating steps may be nested within the advancing steps.

In some embodiments, the individual advances are carried out over anaverage distance of travel for each advance of from 10 or 50 microns to100 or 200 microns (optionally including the total distance of travelfor each vertically reciprocating step, e.g., the sum of the upstrokedistance minus the downstroke distance).

Apparatus for carrying out the invention in which the reciprocationsteps described herein are implemented substantially as described above,with the drive associated with the carrier, and/or with an additionaldrive operatively associated with the transparent member, and with thecontroller operatively associated with either or both thereof andconfigured to reciprocate the carrier and transparent member withrespect to one another as described above.

In the alternative, vertical reciprocation may be carried out byconfiguring the build surface (and corresponding build plate) so that itmay have a limited range of movement up and down in the vertical or “Z”dimension, while the carrier advances (e.g., continuously or step-wise)away from the build plate in the vertical or “Z” dimension. In someembodiments, such limited range of movement may be passively imparted,such as with upward motion achieved by partial adhesion of the buildplate to the growing object through a viscous polymerizable liquid,followed by downward motion achieved by the weight, resiliency, etc. ofthe build plate (optionally including springs, buffers, shock absorbersor the like, configured to influence either upward or downward motion ofthe build plate and build surface). In another embodiment, such motionof the build surface may be actively achieved, by operativelyassociating a separate drive system with the build plate, which drivesystem is also operatively associated with the controller, to separatelyachieve vertical reciprocation. In still another embodiment, verticalreciprocation may be carried out by configuring the build plate, and/orthe build surface, so that it flexes upward and downward, with theupward motion thereof being achieved by partial adhesion of the buildsurface to the growing object through a viscous polymerizable liquid,followed by downward motion achieved by the inherent stiffness of thebuild surface biasing it or causing it to return to a prior position.

It will be appreciated that illumination or irradiation steps, whenintermittent, may be carried out in a manner synchronized with verticalreciprocation, or not synchronized with vertical reciprocation,depending on factors such as whether the reciprocation is achievedactively or passively.

It will also be appreciated that vertical reciprocation may be carriedout between the carrier and all regions of the build surfacesimultaneously (e.g., where the build surface is rigid), or may becarried out between the carrier and different regions of the buildsurface at different times (e.g., where the build surface is of aflexible material, such as a tensioned polymer film).

6. Increased Speed of Fabrication by Increasing Light Intensity.

In general, it has been observed that speed of fabrication can increasewith increased light intensity. In some embodiments, the light isconcentrated or “focused” at the build region to increase the speed offabrication. This may be accomplished using an optical device such as anobjective lens.

The speed of fabrication may be generally proportional to the lightintensity. For example, the build speed in millimeters per hour may becalculated by multiplying the light intensity in milliWatts per squarecentimeter and a multiplier. The multiplier may depend on a variety offactors, including those discussed below. A range of multipliers, fromlow to high, may be employed. On the low end of the range, themultiplier may be about 10, 15, 20 or 30. On the high end of themultiplier range, the multiplier may be about 150, 300, 400 or more.

The relationships described above are, in general, contemplated forlight intensities of from 1, 5 or 10 milliWatts per square centimeter,up to 20 or 50 milliWatts per square centimeter.

Certain optical characteristics of the light may be selected tofacilitate increased speed of fabrication. By way of example, a bandpass filter may be used with a mercury bulb light source to provide365±10 nm light measured at Full Width Half Maximum (FWHM). By way offurther example, a band pass filter may be used with an LED light sourceto provide 375±15 nm light measured at FWHM.

As noted above, polymerizable liquids used in such processes are, ingeneral, free radical polymerizable liquids with oxygen as theinhibitor, or acid-catalyzed or cationically polymerizable liquids witha base as the inhibitor. Some specific polymerizable liquids will ofcourse cure more rapidly or efficiently than others and hence be moreamenable to higher speeds, though this may be offset at least in part byfurther increasing light intensity.

At higher light intensities and speeds, the “dead zone” may becomethinner as inhibitor is consumed. If the dead zone is lost then theprocess will be disrupted. In such case, the supply of inhibitor may beenhanced by any suitable means, including providing an enriched and/orpressurized atmosphere of inhibitor, a more porous semipermeable member,a stronger or more powerful inhibitor (particularly where a base isemployed), etc.

In general, lower viscosity polymerizable liquids are more amenable tohigher speeds, particularly for fabrication of articles with a largeand/or dense cross section (although this can be offset at least in partby increasing light intensity). Polymerizable liquids with viscositiesin the range of 50 or 100 centipoise, up to 600, 800 or 1000 centipoiseor more (as measured at room temperature and atmospheric pressure with asuitable device such as a HYDRAMOTION REACTAVISC™ Viscometer (availablefrom Hydramotion Ltd, 1 York Road Business Park, Malton, York Y017 6YAEngland). In some embodiments, where necessary, the viscosity of thepolymerizable liquid can advantageously be reduced by heating thepolymerizable liquid, as described above.

In some embodiments, such as fabrication of articles with a large and/ordense cross-section, speed of fabrication can be enhanced by introducingreciprocation to “pump” the polymerizable liquid, as described above,and/or the use of feeding the polymerizable liquid through the carrier,as also described above, and/or heating and/or pressurizing thepolymerizable liquid, as also described above.

7. Tiling.

It may be desirable to use more than one light engine to preserveresolution and light intensity for larger build sizes. Each light enginemay be configured to project an image (e.g., an array of pixels) intothe build region such that a plurality of “tiled” images are projectedinto the build region. As used herein, the term “light engine” can meanan assembly including a light source, a DLP device such as a digitalmicromirror device and an optical device such as an objective lens. The“light engine” may also include electronics such as a controller that isoperatively associated with one or more of the other components.

In some embodiments, a configuration with the overlapped images isemployed with some faun of “blending” or “smoothing” of the overlappedregions as generally discussed in, for example, U.S. Pat. Nos.7,292,207, 8,102,332, 8,427,391, 8,446,431 and U.S. Patent ApplicationPublication Nos. 2013/0269882, 2013/0278840 and 2013/0321475, thedisclosures of which are incorporated herein in their entireties.

The tiled images can allow for larger build areas without sacrificinglight intensity, and therefore can facilitate faster build speeds forlarger objects. It will be understood that more than two light engineassemblies (and corresponding tiled images) may be employed. Variousembodiments of the invention employ at least 4, 8, 16, 32, 64, 128 ormore tiled images.

8. Fabrication in Multiple Zones.

As noted above, embodiments of the invention may carry out the formationof the three-dimensional object through multiple zones or segments ofoperation. Such a method generally comprises:

(a) providing a carrier and an optically transparent member having abuild surface, the carrier and the build surface defining a build regiontherebetween, with the carrier positioned adjacent and spaced apart fromthe build surface at a start position; then

(b) forming an adhesion segment of the three-dimensional object by:

-   -   (i) filling the build region with a polymerizable liquid,    -   (ii) irradiating the build region with light through the        optically transparent member (e.g., by a single exposure), while    -   (iii) maintaining the carrier stationary or advancing the        carrier away from the build surface at a first cumulative rate        of advance, to thereby form from the polymerizable liquid a        solid polymer adhesion segment of the object adhered to the        carrier; then

(c) optionally but preferably forming a transition segment of the threedimensional object by

-   -   (i) filling the build region with a polymerizable liquid,    -   (ii) continuously or intermittently irradiating the build region        with light through the optically transparent member, and    -   (iii) continuously or intermittently advancing (e.g.,        sequentially or concurrently with the irradiating step) the        carrier away from the build surface at a second cumulative rate        of advance to thereby form from the polymerizable liquid a        transition segment of the object between the adhesion segment        and the build surface;    -   wherein the second cumulative rate of advance is greater than        the first cumulative rate of advance; and then

(d) forming a body segment of the three dimensional object by:

-   -   (i) filling the build region with a polymerizable liquid,    -   (ii) continuously or intermittently irradiating the build region        with light through the optically transparent, and    -   (iii) continuously or intermittently advancing (e.g.,        sequentially or concurrently with the irradiating step) the        carrier away from the build surface at a third cumulative rate        of advance, to thereby form from the polymerizable liquid a body        segment of the object between the transition segment and the        build surface;    -   wherein the third cumulative rate of advance is greater than the        first and/or the second cumulative rate of advance.

Note that the start position can be any position among a range ofpositions (e.g., a range of up to 5 or 10 millimeters or more), and theirradiating step (b)(ii) is carried out at an intensity sufficient toadhere the solid polymer to the carrier when the carrier is at anyposition within that range of positions. This advantageously reduces thepossibility of failure of adhesion of the three-dimensional object tothe carrier due to variations in uniformity of the carrier and/or buildsurfaces, variations inherent in drive systems in positioning thecarrier adjacent the build surface, etc.

9. Fabrication with Intermittent (or Strobe″) Illumination.

As noted above, in some embodiments the invention may be carried outwith the illumination in intermittent periods or burst. In oneembodiment, such a method comprises:

providing a carrier and an optically transparent member having a buildsurface, the carrier and the build surface defining a build regiontherebetween;

filling the build region with a polymerizable liquid,

intermittently irradiating the build region with light through theoptically transparent member to form a solid polymer from thepolymerizable liquid,

continuously advancing the carrier away from the build surface to formthe three-dimensional object from the solid polymer.

Another embodiment of such a mode of operation comprises:

providing a carrier and an optically transparent member having a buildsurface, the carrier and the build surface defining a build regiontherebetween;

filling the build region with a polymerizable liquid,

intermittently irradiating the build region with light through theoptically transparent member to form a solid polymer from thepolymerizable liquid,

continuously or intermittently advancing (e.g., sequentially orconcurrently with the irradiating step) the carrier away from the buildsurface to form the three-dimensional object from the solid polymer.

In some embodiments, the intermittently irradiating comprisesalternating periods of active and inactive illumination, where theaverage duration of the periods of active illumination is less than theaverage duration of the periods of inactive illumination (e.g., is notmore than 50, 60, or 80 percent thereof).

In other embodiments, the intermittently irradiating comprisesalternating periods of active and inactive illumination, where theaverage duration of the periods of active illumination is the same as orgreater than the average duration of the periods of inactiveillumination (e.g., is at least 100, 120, 160, or 180 percent thereof).

Examples of such modes of operation are given further below. Thesefeatures may be combined with any of the other features and operatingsteps or parameters described herein.

10. Fabrication of Body Segment by Multiple Operating Modes.

Operating modes (that is, the pattern defining the manner of irradiatingand advancing) may be changed in the course of fabricating a threedimensional object (i.e., the major portion, or “body portion”,thereof), to best suit the particular geometry of each contiguoussegment of that three-dimensional object, particularly as that geometrychanges during the course of fabrication.

In general, base and transition zones may still be fabricated asdescribed above, as the preferred foundation for the body of that objectduring fabrication thereof.

Horizontal portions of the three, dimensional object, abrupt changes incross section, and converging or diverging elements of the threedimensional object, may be fabricated in a reciprocal or oscillatoryoperating mode, for example, to eliminate surface defects, such aspitting, and speed or enhance resin replenishment to the build region.

Vertical and thin-walled sections of the three dimensional object, andfragile elements or fine features thereof, can be fabricated in acontinuous operating mode. In some embodiments, continuous mode is leastconcussive of the various operating modes, and hence is better suited tofabricating segments of three-dimensional objects with complex ordelicate geometries (though this may be influenced by the choice ofmaterials for the build surface—that is, rigid vs. flexible).

Feathering, or gradual transitioning of operating mode parameters, maybe included in the course of changing operating modes (that is, betweenone operating mode and a subsequent operating mode). For example, in anintra-oscillatory build: oscillatory parameters are driven by enablingresin flow and allow time for the resin level in the build area toequilibrate—for thinner cross-sections, one can use a lower oscillationheight, faster oscillation speeds, and/or smaller delay time toreplenish resin, while the opposite is true for thicker cross-sections.

In feathering from an reciprocal (or oscillatory) to continuousoperating mode: A pause following oscillatory mode, ramp in continuousspeed from 10 mm/hr to standard continuous speed as analog to transitionzone, effective dosage to initial slices drops from “over-exposed”(allowing proper adhesion) to the recommended dosage.

In feathering from continuous to oscillatory: initial oscillationdisplacement following transition accounts for area of last exposedcontinuous frame, e.g. high oscillation displacement for largecross-section and vice versa. Dosage for initial frames can be constantor ramped from high to low.

In an alternative to changing operating modes (or in combination withchanging operating modes), the parameters of an operating mode can bechanged during formation of the three-dimensional object. Examples ofparameters that can be changed include, for example, frequency ofirradiating, intensity of irradiating, duration of irradiating, dutycycle of irradiating, rate of advancing, lead time prior to irradiating,lag time following irradiating, step height, pump height, step or pumpduration, or frequency of step-wise or reciprocal advancing. Forexample:

greater pump height may be preferred for fabricating a dense portion orsegments of an object (such as a completely solid portion, or a densefoam or lattice portion);

greater pump speed may be preferred for a sparse (or less dense) segmentor portion of an object, such as a hollow, mesh-filled, open foam oropen lattice portion of an object; and

decreased lead and lag times may be preferred when overall speed or rateof formation is increased.

Additional reasons for varying such parameters are indicated above andbelow.

It will be appreciated that the pattern of exposure may be changed inthe course of fabrication, e.g., from slice to slice, to alter thegeometry of external surfaces of the three-dimensional object, to alterthe geometry of internal surfaces of the three dimensional object forstructural purposes, to alter the geometry of internal surfaces of theobject to change micro-structure or material properties of the object(e.g., in the formation of a regular or irregular mesh, lattice, or foam(including open and closed cell foams), to maintain or alter flow of thepolymerizable liquid to the build region, etc. In addition, in thepresent invention, slice thickness may advantageously be varied, asdiscussed further below.

11. Varying Slice Thickness.

As noted above, the methods and processes described hereinadvantageously accommodate input in varying slice thickness, rather thana fixed slice thickness, during formation of a three-dimensional object,allowing the operation of the methods and apparatus to be simplified,and particularly for electronic or computer-generated instructions tothe apparatus for carrying out the method to be simplified. For example,for an object that includes both finely detailed portions as well asless detailed portions, or relatively constant portions, slice thicknesscan be thinner for the detailed portions, and thicker for the relativelyconstant portions.

The number of times slice thickness is changed will depend upon factorssuch as the object material and properties, geometry, tensile or othermaterial properties, tolerances, etc. There are no particular limits,and hence in some embodiments, slice thickness may be changed at least2, 4, 8 or 10 times during formation of the object or object bodyportion (and optionally up to 100 or 1000 times, or more). Note thatevery change may not be to a different slice thickness, but may in someinstances be a reversion to a previous (but not the immediatelyprevious) slice thickness.

For example, in some embodiments, changing may be between: at least oneslice having a thickness of less than 2 or 4 microns; optionally atleast one slice having a thickness between 40 and 80 microns; and atleast one slice having a thickness of more than 200, 400 or 600 microns.

In some embodiments, changing may be between: at least one slice havinga thickness of less than 2 or 4 microns; and at least one slice having athickness of more than 40 or 80 microns.

In some embodiments, the changing may be between at least one slicehaving a thickness of less than 20 or 40 microns; optionally at leastone slice having a thickness between 60 and 80 microns; and at least oneslice having a thickness of more than 200, 400, or 600 microns.

In some embodiments, the changing may be between at least a first thinslice and a second thicker slice, wherein said second slice has athickness at least 5, 10, 15 or 20 times greater than said first slice.

In some embodiments, the changing is between at least a first plurality(e.g., at least 2, 5, 10 or 20) of contiguous thin slices and a secondthicker slice, wherein each of said thin slices is different from oneanother, and wherein said second thicker slice has a thickness at least5, 10, 15, or 20 times greater than each of said plurality of thinslices.

Variation of slice thickness may be implemented in any operating mode,as discussed further below, and in combination with changing operatingmodes in the course of fabricating a particular three-dimensionalobject, as also discussed further below.

12. Dual Hardening Polymerizable Liquids: Part B.

As noted above, in some embodiments of the invention, the polymerizableliquid comprises a first light polymerizable component (sometimesreferred to as “Part A” herein) and a second component that solidifiesby another mechanism, or in a different manner from, the first component(sometimes referred to as “Part B” herein), typically by furtherreacting, polymerizing, or chain extending. Numerous embodiments thereofmay be carried out. In the following, note that, where particularacrylates such as methacrylates are described, other acrylates may alsobe used.

Part A chemistry. As noted above, in some embodiments of the presentinvention, a resin will have a first component, termed “Part A.” Part Acomprises or consists of a mix of monomers and/or prepolymers that canbe polymerized by exposure to actinic radiation or light. This resin canhave a functionality of 2 or higher (though a resin with a functionalityof 1 can also be used when the polymer does not dissolve in itsmonomer). A purpose of Part A is to “lock” the shape of the object beingformed or create a scaffold for the one or more additional components(e.g., Part B). Importantly, Part A is present at or above the minimumquantity needed to maintain the shape of the object being formed afterthe initial solidification. In some embodiments, this amount correspondsto less than ten, twenty, or thirty percent by weight of the total resin(polymerizable liquid) composition.

In some embodiments, Part A can react to form a cross-linked polymernetwork or a solid homopolymer.

Examples of suitable reactive end groups suitable for Part Aconstituents, monomers, or prepolymers include, but are not limited to:acrylates, methacrylates, a-olefins, N-vinyls, acrylamides,methacrylamides, styrenics, epoxides, thiols, 1,3-dienes, vinyl halides,acrylonitriles, vinyl esters, maleimides, and vinyl ethers.

An aspect of the solidification of Part A is that it provides a scaffoldin which a second reactive resin component, termed “Part B,” cansolidify during a second step (which may occur concurrently with orfollowing the solidification of Part A). This secondary reactionpreferably occurs without significantly distorting the original shapedefined during the solidification of Part A. Alternative approacheswould lead to a distortion in the original shape in a desired manner.

In particular embodiments, when used in the methods and apparatusdescribed herein, the solidification of Part A is continuously inhibitedduring printing within a certain region, by oxygen or amines or otherreactive species, to form a liquid interface between the solidified partand an inhibitor-permeable film or window (e.g., is carried out bycontinuous liquid interphase/interface printing).

Part B chemistry. Part B may comprise, consist of or consist essentiallyof a mix of monomers and/or prepolymers that possess reactive end groupsthat participate in a second solidification reaction after the Part Asolidification reaction. In some embodiments, Part B could be addedsimultaneously to Part A so it is present during the exposure toactinide radiation, or Part B could be infused into the object madeduring the 3D printing process in a subsequent step. Examples of methodsused to solidify Part B include, but are not limited to, contacting theobject or scaffold to heat, water or water vapor, light at a differentwavelength than that at which Part A is cured, catalysts, (with orwithout additional heat), evaporation of a solvent from thepolymerizable liquid (e.g., using heat, vacuum, or a combinationthereof), microwave irradiation, etc., including combinations thereof.

Examples of suitable reactive end group pairs suitable for Part Bconstituents, monomers or prepolymers include, but are not limited to:epoxy/amine, epoxy/hydroxyl, oxetane/amine, oxetane/alcohol,isocyanate*/hydroxyl, Isocyanate*/amine, isocyanate/carboxylic acid,anhydride/amine, amine/carboxylic acid, amine/ester, hydroxyl/carboxylicacid, hydroxyl/acid chloride, amine/acid chloride, vinyl/Si—H(hydrosilylation), Si—Cl/hydroxyl, Si—Cl/amine, hydroxyl/aldehyde,amine/aldehyde, hydroxymethyl or alkoxymethyl amide/alcohol, aminoplast,alkyne/Azide (also known as one embodiment of “Click Chemistry,” alongwith additional reactions including thiolene, Michael additions,Diels-Alder reactions, nucleophilic substitution reactions, etc.),alkene/Sulfur (polybutadiene vulcanization), alkene/peroxide,alkene/thiol, alkyne/thiol, hydroxyl/halide, isocyanate*/water(polyurethane foams), Si—OH/hydroxyl, Si—OH/water, Si—OH/Si—H (tincatalyzed silicone), Si—OH/Si—OH (tin catalyzed silicone),Perfluorovinyl (coupling to form perfluorocyclobutane), etc., where*Isocyanates include protected isocyanates (e.g. oximes)),diene/dienophiles for Diels-Alder reactions, olefin metathesispolymerization, olefin polymerization using Ziegler-Natta catalysis,ring-opening polymerization (including ring-opening olefin metathesispolymerization, lactams, lactones, Siloxanes, epoxides, cyclic ethers,imines, cyclic acetals, etc.), etc.

Other reactive chemistries suitable for Part B will be recognizable bythose skilled in the art. Part B components useful for the formation ofpolymers described in “Concise Polymeric Materials Encyclopedia” and the“Encyclopedia of Polymer Science and Technology” are hereby incorporatedby reference.

Organic peroxides. In some embodiments, an organic peroxide may beincluded in the polymerizable liquid or resin, for example to facilitatethe reaction of potentially unreacted double bonds during heat and/ormicrowave irradiation curing. Such organic peroxides may be included inthe resin or polymerizable liquid in any suitable amount, such as from0.001 or 0.01 or 0.1 percent by weight, up to 1, 2, or 3 percent byweight. Examples of suitable organic peroxides include, but are notlimited to, 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane (e.g., LUPEROX101™), dilauroyl peroxide (e.g. LUPEROX LP™) benzoyl peroxide (e.g.,LUPEROX A98™), and bis(tert-butyldioxyisopropyl)benzene (e.g., VulCUPR™), etc., including combinations thereof Such organic peroxides areavailable from a variety of sources, including but not limited to Arkema(420 rue d'Estienne d'Orves, 92705 Colombes Cedex, France).

Elastomers. A particularly useful embodiment for implementing theinvention is for the formation of elastomers. Tough, high-elongationelastomers are difficult to achieve using only liquid UV-curableprecursors. However, there exist many thermally cured materials(polyurethanes, silicones, natural rubber) that result in tough,high-elongation elastomers after curing. These thermally curableelastomers on their own are generally incompatible with most 3D printingtechniques.

In embodiments of the current invention, small amounts (e.g., less than20 percent by weight) of a low-viscosity UV curable material (Part A)are blended with thermally-curable precursors to form (preferably tough)elastomers (e.g. polyurethanes, polyureas, or copolymers thereof (e.g.,poly(urethane-urea)), and silicones) (Part B). The UV curable componentis used to solidify an object into the desired shape using 3D printingas described herein and a scaffold for the elastomer precursors in thepolymerizable liquid. The object can then be heated after printing,thereby activating the second component, resulting in an objectcomprising the elastomer.

Adhesion of formed objects. In some embodiments, it may be useful todefine the shapes of multiple objects using the solidification of PartA, align those objects in a particular configuration, such that there isa hermetic seal between the objects, then activate the secondarysolidification of Part B. In this manner, strong adhesion between partscan be achieved during production. A particularly useful example may bein the formation and adhesion of sneaker components.

Fusion of particles as Part B. In some embodiments, “Part B” may simplyconsist of small particles of a pre-formed polymer. After thesolidification of Part A, the object may be heated above the glasstransition temperature of Part B in order to fuse the entrappedpolymeric particles.

Evaporation of solvent as Part B. In some embodiments, “Part B” mayconsist of a pre-formed polymer dissolved in a solvent. After thesolidification of Part A into the desired object, the object issubjected to a process (e.g. heat+vacuum) that allows for evaporation ofthe solvent for Part B, thereby solidifying Part B.

Thermally cleavable end groups. In some embodiments, the reactivechemistries in Part A can be thermally cleaved to generate a newreactive species after the solidification of Part A. The newly formedreactive species can further react with Part B in a secondarysolidification. An exemplary system is described by Velankar, Pezos andCooper, Journal of Applied Polymer Science, 62, 1361-1376 (1996). Here,after UV-curing, the acrylate/methacrylate groups in the formed objectare thermally cleaved to generated diisocyanate prepolymers that furtherreact with blended chain-extender to give high molecular weightpolyurethanes/polyureas within the original cured material or scaffold.Such systems are, in general, dual-hardening systems that employ blockedor reactive blocked prepolymers, as discussed in greater detail below.It may be noted that later work indicates that the thermal cleavageabove is actually a displacement reaction of the chain extender (usuallya diamine) with the hindered urea, giving the finalpolyurethanes/polyureas without generating isocyanate intermediates.

Methods of mixing components. In some embodiments, the components may bemixed in a continuous manner prior to being introduced to the printerbuild plate. This may be done using multi-barrel syringes and mixingnozzles. For example, Part A may comprise or consist of a UV-curabledi(meth)acrylate resin, Part B may comprise or consist of a diisocyanateprepolymer and a polyol mixture. The polyol can be blended together inone barrel with Part A and remain unreacted. A second syringe barrelwould contain the diisocyanate of Part B. In this manner, the materialcan be stored without worry of “Part B” solidifying prematurely.Additionally, when the resin is introduced to the printer in thisfashion, a constant time is defined between mixing of all components andsolidification of Part A.

Additional examples of “dual cure” polymerizable liquids (or “resins”),and methods that may be used in carrying out the present inventioninclude, but are not limited to, those set forth in J. Rolland et al.,Method of Producing Polyurethane Three-Dimensional Objects fromMaterials having Multiple Mechanisms of Hardening, PCT Publication No.WO 2015/200179 (published 30 Dec. 2015); J. Rolland et al., Methods ofProducing Three-Dimensional Objects from Materials Having MultipleMechanisms of Hardening, PCT Publication No. WO 2015/200173 (published30 Dec. 2015); J. Rolland et al., Three-Dimensional Objects Producedfrom Materials Having Multiple Mechanisms of Hardening, PCT PublicationNo. WO/2015/200189 (published 30 Dec. 2015); J. Rolland et al.,Polyurethane Resins Having Multiple Mechanisms of Hardening for Use inProducing Three-Dimensional Objects published 30 Dec. 2015); and

J. Rolland et al., Method of Producing Three-Dimensional Objects fromMaterials having Multiple Mechanisms of Hardening, U.S. patentapplication Ser. No. 14/977,822 (filed 22 Dec. 2015); J. Rolland et al.,Method of Producing Polyurethane Three-Dimensional Objects fromMaterials having Multiple Mechanisms of Hardening, U.S. patentapplication Ser. No. 14/977,876 (filed 22 Dec. 2015), J. Rolland et al.,Three-Dimensional Objects Produced from Materials having MultipleMechanisms of Hardening U.S. patent application Ser. No. 14/977,938(filed 22 Dec. 2015), and J. Rolland et al., Polyurethane Resins havingMultiple Mechanisms of Hardening for Use in Producing Three-DimensionalObjects, U.S. patent application Ser. No. 14/977,974 (filed 22 Dec.2015);

The disclosures of all of which are incorporated by reference herein intheir entirety.

13. Fabrication Products.

Three-dimensional products produced by the methods and processes of thepresent invention may be final, finished or substantially finishedproducts, or may be intermediate products subject to furthermanufacturing steps such as surface treatment, laser cutting, electricdischarge machining, etc., is intended. Intermediate products includeproducts for which further additive manufacturing, in the same or adifferent apparatus, may be carried out). For example, a fault orcleavage line may be introduced deliberately into an ongoing “build” bydisrupting, and then reinstating, the gradient of polymerization zone,to terminate one region of the finished product, or simply because aparticular region of the finished product or “build” is less fragilethan others.

Numerous different products can be made by the methods and apparatus ofthe present invention, including both large-scale models or prototypes,small custom products, miniature or microminiature products or devices,etc. Examples include, but are not limited to, medical devices andimplantable medical devices such as stents, drug delivery depots,functional structures, microneedle arrays, fibers and rods such aswaveguides, micromechanical devices, microfluidic devices, etc.

Thus in some embodiments the product can have a height of from 0.1 or 1millimeters up to 10 or 100 millimeters, or more, and/or a maximum widthof from 0.1 or 1 millimeters up to 10 or 100 millimeters, or more. Inother embodiments, the product can have a height of from 10 or 100nanometers up to 10 or 100 microns, or more, and/or a maximum width offrom 10 or 100 nanometers up to 10 or 100 microns, or more. These areexamples only: Maximum size and width depends on the architecture of theparticular device and the resolution of the light source and can beadjusted depending upon the particular goal of the embodiment or articlebeing fabricated.

In some embodiments, the ratio of height to width of the product is atleast 2:1, 10:1, 50:1, or 100:1, or more, or a width to height ratio of1:1, 10:1, 50:1, or 100:1, or more.

In some embodiments, the product has at least one, or a plurality of,pores or channels formed therein, as discussed further below.

The processes described herein can produce products with a variety ofdifferent properties. Hence in some embodiments the products are rigid;in other embodiments the products are flexible or resilient. In someembodiments, the products are a solid; in other embodiments, theproducts are a gel such as a hydrogel. In some embodiments, the productshave a shape memory (that is, return substantially to a previous shapeafter being deformed, so long as they are not deformed to the point ofstructural failure). In some embodiments, the products are unitary (thatis, Rained of a single polymerizable liquid); in some embodiments, theproducts are composites (that is, formed of two or more differentpolymerizable liquids). Particular properties will be determined byfactors such as the choice of polymerizable liquid(s) employed.

In some embodiments, the product or article made has at least oneoverhanging feature (or “overhang”), such as a bridging element betweentwo supporting bodies, or a cantilevered element projecting from onesubstantially vertical support body. Because of the unidirectional,continuous nature of some embodiments of the present processes, theproblem of fault or cleavage lines that form between layers when eachlayer is polymerized to substantial completion and a substantial timeinterval occurs before the next pattern is exposed, is substantiallyreduced. Hence, in some embodiments the methods are particularlyadvantageous in reducing, or eliminating, the number of supportstructures for such overhangs that are fabricated concurrently with thearticle.

14. Additional and Alternate Methods and Apparatus.

Additional examples of apparatus, polymerizable liquids (or “resins”),and methods that may be used in carrying out the present inventioninclude, but are not limited to, those set forth in J. DeSimone et al.,Three-Dimensional Printing Using Tiled Light Engines, PCT PublicationNo. WO/2015/195909 (published 23 Dec. 2015); J. DeSimone et al.,Three-Dimensional Printing Method Using Increased Light Intensity andApparatus Therefore, PCT Publication No. WO/2015/195920 (published 23Dec. 2015), A. Ermoshkin et al., Three-Dimensional Printing withReciprocal Feeding of Polymerizable Liquid, PCT Publication No.WO/2015/195924 (published 23 Dec. 2015); J. Rolland et al., Method ofProducing Polyurethane Three-Dimensional Objects from Materials havingMultiple Mechanisms of Hardening, PCT Publication No. WO 2015/200179(published 30 Dec. 2015); J. Rolland et al., Methods of ProducingThree-Dimensional Objects from Materials Having Multiple Mechanisms ofHardening, PCT Publication No. WO 2015/200173 (published 30 Dec. 2015);

J. Rolland et al., Three-Dimensional Objects Produced from MaterialsHaving Multiple Mechanisms of Hardening, PCT Publication No.WO/2015/200189 (published 30 Dec. 2015); J. Rolland et al., PolyurethaneResins Having Multiple Mechanisms of Hardening for Use in ProducingThree-Dimensional Objects published 30 Dec. 2015); and J. DeSimone etal., Methods and Apparatus for Continuous Liquid Interface Productionwith Rotation, PCT Publication No. WO/2016/007495, the disclosures ofwhich are incorporated by reference herein in their entirety.

In an alternate embodiment of the invention, the methods may be carriedout with a method and apparatus as described in Hull, U.S. Pat. No.5,236,637, at FIG. 4, where the polymerizable liquid is floated on topof an immiscible liquid layer (said to be “non-wetting” therein). Here,the immiscible liquid layer serves as the build surface. If soimplemented, the immiscible liquid (which may be aqueous or non-aqueous)preferably: (i) has a density greater than the polymerizable liquid,(ii) is immiscible with the polymerizable liquid, and (iii) is wettablewith the polymerizable liquid. Ingredients such as surfactants, wettingagents, viscosity-enhancing agents, pigments, and particles mayoptionally be included in either or both of the polymerizable liquid orimmiscible liquid.

While the present invention is preferably carried out by continuousliquid interphase polymerization, as described in detail above, in someembodiments alternate methods and apparatus for bottom-upthree-dimension fabrication may be used, including layer-by-layerfabrication. Examples of such methods and apparatus include, but are notlimited to, those described U.S. Pat. No. 7,438,846 to John and U.S.Pat. No. 8,110,135 to El-Siblani, and in U.S. Patent ApplicationPublication Nos. 2013/0292862 to Joyce and 2013/0295212 to Chen et al.The disclosures of these patents and applications are incorporated byreference herein in their entirety.

The present invention is explained in greater detail in the followingnon-limiting Examples.

EXAMPLE 1 Continuous Fabrication with Intermittent Irradiation andAdvancing

A process of the present invention is illustrated in FIG. 6, where thevertical axis illustrates the movement of the carrier away from thebuild surface. In this embodiment, the vertical movement or advancingstep (which can be achieved by driving either the carrier or the buildsurface, preferably the carrier), is continuous and unidirectional, andthe irradiating step is carried out continuously. Polymerization of thearticle being fabricated occurs from a gradient of polymerization oractive surface, and hence creation of “layer by layer” fault lineswithin the article is minimized.

An alternate embodiment of the present invention is illustrated in FIG.7. In this embodiment, the advancing step is carried out in astep-by-step manner, with pauses introduced between active advancing ofthe carrier and build surface away from one another. In addition, theirradiating step is carried out intermittently, in this case during thepauses in the advancing step. We find that, as long as the inhibitor ofpolymerization is supplied to the dead zone in an amount sufficient tomaintain the dead zone and the adjacent gradient of polymerization oractive surface during the pauses in irradiation and/or advancing, thegradient of polymerization is maintained, and the formation of layerswithin the article of manufacture is minimized or avoided. Stateddifferently, the polymerization is continuous, even though theirradiating and advancing steps are not. Sufficient inhibitor can besupplied by any of a variety of techniques, including but not limitedto: utilizing a transparent member that is sufficiently permeable to theinhibitor, enriching the inhibitor (e.g., feeding the inhibitor from aninhibitor-enriched and/or pressurized atmosphere), etc. In general, themore rapid the fabrication of the three-dimensional object (that is, themore rapid the cumulative rate of advancing), the more inhibitor will berequired to maintain the dead zone and the adjacent gradient ofpolymerization.

EXAMPLE 2 Continuous Fabrication with Reciprocation During Advancing toEnhance Filling of Build Region with Polymerizable Liquid

A still further embodiment of the present invention is illustrated inFIG. 8. As in Example 10 above, this embodiment, the advancing step iscarried out in a step-by-step manner, with pauses introduced betweenactive advancing of the carrier and build surface away from one another.Also as in Example 1 above, the irradiating step is carried outintermittently, again during the pauses in the advancing step. In thisexample, however, the ability to maintain the dead zone and gradient ofpolymerization during the pauses in advancing and irradiating is takenadvantage of by introducing a vertical reciprocation during the pausesin irradiation.

We find that vertical reciprocation (driving the carrier and buildsurface away from and then back towards one another), particularlyduring pauses in irradiation, serves to enhance the filling of the buildregion with the polymerizable liquid, apparently by pullingpolymerizable liquid into the build region. This is advantageous whenlarger areas are irradiated or larger parts are fabricated, and fillingthe central portion of the build region may be rate-limiting to anotherwise rapid fabrication.

Reciprocation in the vertical or Z axis can be carried out at anysuitable speed in both directions (and the speed need not be the same inboth directions), although it is preferred that the speed whenreciprocating away is insufficient to cause the formation of gas bubblesin the build region.

While a single cycle of reciprocation is shown during each pause inirradiation in FIG. 8, it will be appreciated that multiple cycles(which may be the same as or different from one another) may beintroduced during each pause.

As in Example 1 above, as long as the inhibitor of polymerization issupplied to the dead zone in an amount sufficient to maintain the deadzone and the adjacent gradient of polymerization during thereciprocation, the gradient of polymerization is maintained, theformation of layers within the article of manufacture is minimized oravoided, and the polymerization/fabrication remains continuous, eventhough the irradiating and advancing steps are not.

EXAMPLE 3 Acceleration During Reciprocation Upstroke and DecelerationDuring Reciprocation Downstroke to Enhance Part Quality

We observe that there is a limiting speed of upstroke, and correspondingdownstroke, which if exceeded causes a deterioration of quality of thepart or object being fabricated (possibly due to degradation of softregions within the gradient of polymerization caused by lateral shearforces a resin flow). To reduce these shear forces and/or enhance thequality of the part being fabricated, we introduce variable rates withinthe upstroke and downstroke, with gradual acceleration occurring duringthe upstroke and gradual deceleration occurring during the downstroke,as schematically illustrated in FIG. 9.

EXAMPLE 4 Fabrication in Multiple Zones

FIG. 10 schematically illustrates the movement of the carrier (z) overtime (t) in the course of fabricating a three-dimensional object bymethods as described above, through a first base (or “adhesion”) zone,an optional second transition zone, and a third body zone. The overallprocess of forming the three-dimensional object is thus divided intothree (or two) immediately sequential segments or zones. The zones arepreferably carried out in a continuous sequence without pausesubstantial delay (e.g., greater than 5 or 10 seconds) between the threezones, preferably so that the gradient of polymerization is notdisrupted between the zones.

The first base (or “adhesion”) zone includes an initial light orirradiation exposure at a higher dose (longer duration and/or greaterintensity) than used in the subsequent transition and/or body zones.This is to obviate the problem of the carrier not being perfectlyaligned with the build surface, and/or the problem of variation in thepositioning of the carrier from the build surface, at the start of theprocess, by insuring that the resin is securely polymerized to thecarrier. Note an optional reciprocation step (for initial distributingor pumping of the polymerizable liquid in or into the build region) isshown before the carrier is positioned in its initial, start, position.Note that a release layer (not shown) such as a soluble release layermay still be included between the carrier and the initial polymerizedmaterial, if desired. In general, a small or minor portion of thethree-dimensional object is produced during this base zone (e.g., lessthan 1, 2 or 5 percent by volume). Similarly, the duration of this basezone is, in general, a small or minor portion of the sum of thedurations of the base zone, the optional transition zone, and the bodyzone (e.g., less than 1, 2 or 5 percent).

Immediately following the first base zone of the process, there isoptionally (but preferably) a transition zone. In this embodiment, theduration and/or intensity of the illumination is less, and thedisplacement of the oscillatory step less, compared to that employed inthe base zone as described above. The transition zone may (in theillustrated embodiment) proceed through from 2 or 5, up to 50 or moreoscillatory steps and their corresponding illuminations. In general, anintermediate portion (greater than that formed during the base zone, butless than that formed of during the body zone), of the three dimensionalobject is produced during the transition zone (e.g., from 1, 2 or 5percent to 10, 20 or 40 percent by volume). Similarly, the duration ofthis transition zone is, in general, greater than that of the base zone,but less than that of the body zone (e.g., a duration of from 1, 2 or 5percent to 10, 20 or 40 percent that of the sum of the durations of thebase zone, the transition zone, and the body zone (e.g., less than 1, 2or 5 percent).

Immediately following the transition zone of the process (or, if notransition zone is included, immediately following the base zone of theprocess), there is a body zone, during which the remainder of thethree-dimensional object is formed. In the illustrated embodiment, thebody zone is carried out with illumination at a lower dose than the basezone (and, if present, preferably at a lower dose than that in thetransition zone), and the reciprocation steps are (optionally but insome embodiments preferably) carried out at a smaller displacement thanthat in the base zone (and, if present, optionally but preferably at alower displacement than in the transition zone). In general, a majorportion, typically greater than 60, 80, or 90 percent by volume, of thethree-dimensional object is produced during the transition zone.Similarly, the duration of this body zone is, in general, greater thanthat of the base zone and/or transition zone (e.g., a duration of atleast 60, 80, or 90 percent that of the sum of the durations of the basezone, the transition zone, and the body zone).

Note that, in this example, the multiple zones are illustrated inconnection with an oscillating mode of fabrication, but the multiplezone fabrication technique described herein may also be implemented withother modes of fabrication as illustrated further in the examples below(with the transition zone illustrated as included, but again beingoptional).

EXAMPLE 5 Fabrication with Intermittent (or “Strobe”) Illumination

The purpose of a “strobe” mode of operation is to reduce the amount oftime that the light or radiation source is on or active (e.g., to notmore than 80, 70, 60, 50, 40, or 30 percent of the total time requiredto complete the fabrication of the three-dimensional object), andincrease the intensity thereof (as compared to the intensity requiredwhen advancing is carried out at the same cumulative rate of speedwithout such reduced time of active illumination or radiation), so thatthe overall dosage of light or radiation otherwise remains substantiallythe same. This allows more time for resin to flow into the build regionwithout trying to cure it at the same time. The strobe mode techniquecan be applied to any of the existing general modes of operationdescribed herein above, including continuous, stepped, and oscillatorymodes, as discussed further below.

FIG. 11A schematically illustrates one embodiment of continuous mode. Inthe conventional continuous mode, an image is projected and the carrierstarts to move upwards. The image is changed at intervals to representthe cross section of the three-dimensional object being producedcorresponding to the height of the build platform. The speed of themotion of the build platform can vary for a number of reasons. Asillustrated, often there is a base zone where the primary goal is toadhere the object to the build platform, a body zone which has a speedwhich is suitable for the whole object being produced, and a transitionzone which is a gradual transition from the speed and/or dosages of thebase zone to the speeds and/or dosages of the body zone. Note that cureis still carried out so that a gradient of polymerization, whichprevents the formation of layer-by-layer fault lines, in thepolymerizable liquid in the build region, is preferably retained, andwith the carrier (or growing object) remaining in liquid contact withthe polymerizable liquid, as discussed above.

FIG. 11B schematically illustrates one embodiment of strobe continuousmode. In strobe continuous the light intensity is increased but theimage is projected in short flashes or intermittent segments. Theincreased intensity allows the resin to cure more quickly so that theamount of flow during cure is minimal. The time between flashes letsresin flow without being cured at the same time. This can reduceproblems caused by trying to cure moving resin, such as pitting.

In addition, the reduced duty cycle on the light source which isachieved in strobe mode can allow for use of increased intermittentpower. For example: If the intensity for the conventional continuousmode was 5 mW/cm² the intensity could be doubled to 10 mW/cm² and thetime that the image is projected could be reduced to half of the time,or the intensity could be increased 5-fold to 25 mW/cm² and the timecould be reduced to ⅕^(th) of the previous light on time.

FIG. 12A schematically illustrates one embodiment of stepped mode: Inthe conventional stepped mode an image is projected while the buildplatform is stationary (or moving slowly as compared to more rapidmovement in between illumination). When one height increment issufficiently exposed the image is turned off and the build platform ismoved upwards by some increment. This motion can be at one speed or thespeed can vary such as by accelerating from a slow speed when thethickness of uncured resin is thin to faster as the thickness of theuncured resin is thicker. Once the build platform is in the new positionthe image of the next cross section is projected to sufficiently exposethe next height increment.

FIG. 12B schematically illustrates one embodiment of strobe steppedmode: In the strobe stepped mode the light intensity is increased andthe amount of time that the image is projected is reduced. This allowsmore time for resin flow so the overall speed of the print can bereduced or the speed of movement can be reduced. For example: If theintensity for the conventional stepped mode was 5 mW/cm² and the buildplatform moves in increments of 100 um in 1 second and the image isprojected for 1 second the intensity could be doubled to 10 mW/cm², thetime that the image is projected could be reduced to 0.5 seconds, andthe speed of movement could be reduced to 50 um/second, or the time thatthe stage is moving could be reduced to 0.5 seconds. The increasedintensity could be as much as 5 fold or more allowing the time allottedfor image projection to be reduced to ⅕^(th) or less.

FIG. 13A schematically illustrates one embodiment of oscillatory mode:In the oscillatory mode an image is again projected while the buildplatform is stationary (or moving slowly as compared to more rapidmovement in-between illuminations). When one height increment is curedthe image is turned off and the build platform is moved upwards to pulladditional resin into the build zone and then moved back down to thenext height increment above the last cured height. This motion can be atone speed or the speed can vary such as by accelerating from a slowspeed when the thickness of uncured resin is thin to faster as thethickness of the uncured resin is thicker. Once the build platform is inthe new position the image of the next cross section is projected tocure the next height increment.

FIG. 13B illustrates one embodiment of strobe oscillatory mode. In thestrobe oscillatory mode the light intensity is increased and the amountof time that the image is projected is reduced. This allows more timefor resin flow so the overall speed of the print can be reduced or thespeed of movement can be reduced. For example: If the intensity for theconventional oscillatory mode was 5mW/cm² and the build platform movesup by 1 mm and back down to an increment of 100 um above the previousheight in 1 second and the image is projected for 1 second the intensitycould be doubled to 10 mW/cm², the time that the image is projectedcould be reduced to 0.5 seconds, and the speed of movement could bereduced to by half or the time that the stage is moving could be reducedto 0.5 seconds. The increased intensity could be as much as 5 fold ormore allowing the time allotted for image projection to be reduced to⅕th or less. Segment “A” of FIG. 13 is discussed further below.

FIG. 14A illustrates a segment of a fabrication method operated inanother embodiment of strobe oscillatory mode. In this embodiment, theduration of the segment during which the carrier is static is shortenedto close that of the duration of the strobe illumination, so that theduration of the oscillatory segment may—if desired—be lengthened withoutchanging the cumulative rate of advance and the speed of fabrication.

FIG. 14B illustrates a segment of another embodiment of strobeoscillatory mode, similar to that of FIG. 14A, except that the carrieris now advancing during the illumination segment (relatively slowly, ascompared to the upstroke of the oscillatory segment).

EXAMPLE 6 Varying of Process Parameters During Fabrication

In the methods of the Examples above, the operating conditions duringthe body zone are shown as constant throughout that zone. However,various parameters can be altered or modified in the course of the bodyzone or segment, as discussed further below.

A primary reason for altering a parameter during production would bevariations in the cross section geometry of the three-dimensionalobject; that is, smaller (easier to fill), and larger (harder to fill)segments or portions of the same three-dimensional object. For easier tofill segments (e.g., 1-5 mm diameter equivalents), the speed of upwardsmovement could be quick (up to 50-1000 m/hr) and/or the pump heightcould be minimal (e.g., as little at 100 to 300 um). For larger crosssectional segments (e.g., 5-500 mm diameter equivalents) the speed ofupward movement can be slower (e.g., 1-50 mm/hr) and/or the pump heightcan be larger (e.g., 500 to 5000 um). Particular parameters will, ofcourse, vary depending on factors such as illumination intensity, theparticular polymerizable liquid (including constituents thereof such asdye and filler concentrations), the particular build surface employed,etc.

In some embodiments, the overall light dosage (determined by time andintensity) may be reduced as the “bulk” of the cross section beingilluminated increases. Said another way, small points of light may needhigher per unit dosage than larger areas of light. Without wishing to bebound to any specific theory, this may relate to the chemical kinematicsof the polymerizable liquid. This effect could cause us to increase theoverall light dosage for smaller cross sectional diameter equivalents.

In some embodiments, vary the thickness of each height increment betweensteps or pumps can be varied. This could be to increase speed withdecreased resolution requirements (that is, fabricating a portion thatrequires less precision or permits more variability, versus a portion ofthe object that requires greater precision or requires more precise ornarrow tolerances). For example, one could change from 100 um incrementsto 200 um or 400 um increments and group all the curing for theincreased thickness into one time period. This time period may beshorter, the same or longer than the combined time for the equivalentsmaller increments.

In some embodiments, the light dosage (time and/or intensity) deliveredcould be varied in particular cross sections (vertical regions of theobject) or even in different areas within the same cross section orvertical region. This could be to vary the stiffness or density ofparticular geometries. This can, for example, be achieved by changingthe dosage at different height increments, or changing the grayscalepercentage of different zones of each height increment illumination.

Examples of body portion fabrication through multiple zones are given inFIGS. 15A-19.

FIG. 15A is a schematic illustration of the fabrication of athree-dimensional object similar to FIG. 13A, except that the bodysegment is fabricated in two contiguous segments, with the first segmentcarried out in an oscillatory operating mode, and the second segmentcarried out in a continuous operating mode. FIG. 16A is a schematicillustration of the fabrication of a three-dimensional object similar toFIG. 11A, except that the body segment is fabricated in three contiguoussegments, with the first and third segments carried out in a continuousoperating mode, and the second segment carried out in oscillatoryoperating mode. FIG. 17A is a schematic illustration of the fabricationof a three-dimensional object similar to FIG. 16A, except that the basezone, transition zone, and first segment of the body zone are carriedout in a strobe continuous operating mode, the second segment of thebody zone is fabricated in an oscillatory operating mode, and the thirdsegment of the body zone is fabricated in a continuous operating mode.

FIG. 15B, 16B, and 17B are similar to the foregoing, except that steppedor step-wise mode is used in place of oscillatory, or “reciprocal” mode.In general, reciprocal or oscillatory mode is preferred over steppedmode, with reciprocation being achieved entirely through motion of thecarrier, or the combined motion of the carrier and a flexible, ormovable, build surface.

FIG. 18A is a schematic illustration of the fabrication of athree-dimensional object similar to FIG. 11A, except that lightintensity is varied in the course of fabricating the base and transitionzones, and both light intensity and rate of advancing are varied in thecourse of fabricating the body zone. FIG. 18B is a schematicillustration of the fabrication of a three-dimensional object similar toFIG. 17A, except that light is interrupted in an intermittent fashion(dashed line representing light intensity during interrupted segments isfor comparison to FIG. 17A only).

FIG. 19 is a schematic illustration of the fabrication of athree-dimensional object similar to FIG. 11A, except that the mode ofoperation during fabrication of the body segment is changed multipletimes for continuous, to reciprocal, and back. This may be employed notonly to accommodate changes in geometry of the three-dimensional objectduring fabrication, but a relatively constant geometry where the part ishollow, to facilitate replenishment of polymerizable liquid in the buildregion.

FIG. 20 schematically illustrates parameters that may be varied within areciprocal (also referred to as “oscillatory”) operating mode (solidline throughout) or a step operating mode (solid line horizontal linesand dashed lines). Note the parameters that may be varied in these twomodes are similar, except for the absence of a pump height parameter instep mode.

EXAMPLE 7 Varying of Slice Thickness During Fabrication

In the methods of the present invention, slice thickness may be heldconstant or varied in any of the operating modes. Examples are given inFIGS. 21A to 21F, where horizontal dashed lines represent the transitionfrom each contiguous slice (corresponding to different exposure orillumination frames or patterns) during the formation of thethree-dimensional object.

FIG. 21A schematically illustrates a method of the invention carried outin a continuous operating mode, with constant slice thickness andconstant carrier speed, while FIG. 21B schematically illustrates amethod of the invention carried out in a continuous operating mode, withvariable slice thickness with constant carrier speed. In both cases,illumination or exposure is continuous, with slices changing over time.Slice thickness could likewise be varied in an intermittent exposuremode of operation (including strobe mode).

FIG. 21C schematically illustrates a method of the invention carried outin a continuous operating mode, with constant slice thickness andvariable carrier speed, while FIG. 21D schematically illustrates amethod of the invention carried out in continuous operating mode, modewith variable slice thickness and variable carrier speed. Again in bothcases, illumination or exposure is continuous with the slices changingover time, but slice thickness could likewise be varied in anintermittent exposure mode of operation.

FIG. 21E schematically illustrates a method of the invention carried outin reciprocal operating mode, with constant slice thickness, while FIG.21F schematically illustrates a method of the invention carried out inreciprocal operating mode, with variable slice thickness. Bold diagonalhash patterns during the exposure periods are to emphasize slicethickness, and variability thereof in FIG. 21F. In both cases, astep-wise mode of operation could be used in place of a reciprocal modeof operation (see, for example, FIG. 20).

The foregoing is illustrative of the present invention, and is not to beconstrued as limiting thereof The invention is defined by the followingclaims, with equivalents of the claims to be included therein.

1. In a method of forming the body portion of a three-dimensional objectfrom a polymerizable liquid by the process of continuous liquidinterface printing, the process including advancing a carrier for theobject away from a build surface while irradiating a build regionbetween the carrier and build surface in a pattern of advancing andirradiating defined by an operating mode, with the body portion having aplurality of contiguous segments and with said irradiating carried outin sequentially presented slices of exposure, each having a pattern thatcorresponds to a segment of said body portion, which each segment havinga thickness during said forming, the improvement comprising: changingslice thickness among said slices at least once during the formation ofsaid body portion.
 2. The method of claim 1, wherein said changing ischanged at least 2, 4, 8 or 10 times during formation of said bodyportion (and optionally up to 100 or 1000 times, or more).
 3. The methodof claim 1, wherein said changing is between: at least one slice havinga thickness of less than 2 or 4 microns; optionally at least one slicehaving a thickness between 40 and 80 microns; and at least one slicehaving a thickness of more than 200, 400 or 600 microns.
 4. The methodof claim 1, wherein said changing is between: at least one slice havinga thickness of less than 2 or 4 microns; and at least one slice having athickness of more than 40 or 80 microns.
 5. The method of claim 1,wherein said changing is between: at least one slice having a thicknessof less than 20 or 40 microns; optionally at least one slice having athickness between 60 and 80 microns; and at least one slice having athickness of more than 200, 400, or 600 microns.
 6. The method of claim1, wherein said changing is between at least a first thin slice and asecond thicker slice, wherein said second slice has a thickness at least5, 10, 15 or 20 times greater than said first slice.
 7. The method ofclaim 1, wherein said changing is between at least a first plurality ofcontiguous thin slices and a second thicker slice, wherein each of saidthin slices is different from one another, and wherein said secondthicker slice has a thickness at least 5, 10, 15, or 20 times greaterthan each of said plurality of thin slices.
 8. The method of claim 1,wherein said plurality of contiguous segments are geometrically distinctfrom one another.
 9. The method of claim 1, wherein said dead zone,and/or said gradient of polymerization or said active surface, aremaintained through said changing steps.
 10. The method of claim 1,wherein said build surface is fixed and stationary in the lateraldimensions.
 11. The method of claim 1, wherein said advancing is carriedout at a cumulative rate of at least 0.1, 1, 10, 100 or 1000 microns persecond.
 12. The method of claim 1, wherein said optically transparentmember comprises a semipermeable member, and said continuouslymaintaining a dead zone is carried out by feeding an inhibitor ofpolymerization through said optically transparent member in an amountsufficient to maintain said dead zone and said gradient ofpolymerization.
 13. The method of claim 1, wherein said opticallytransparent member is comprised of a semipermeable polymer.
 14. Themethod of claim 1, wherein said gradient of polymerization zone and saiddead zone together have a thickness of from 1 to 1000 microns.
 15. Themethod of claim 1, wherein said gradient of polymerization zone ismaintained for a time of at least 5, 10, 20, or 30 seconds, or at least1 or 2 minutes.
 16. The method of claim 1, further comprising the stepof heating said polymerizable liquid to reduce the viscosity thereof insaid build region.
 17. The method of claim 1, wherein said irradiatingstep is carried out by maskless photolithography.
 18. The method ofclaim 1, wherein: said polymerizable liquid comprises a free radicalpolymerizable liquid and said inhibitor comprises oxygen; or saidpolymerizable liquid comprises an acid-catalyzed or cationicallypolymerizable liquid, and said inhibitor comprises a base.
 19. A methodof claim 1, wherein: said polymerizable liquid comprises a mixture of(i) a light polymerizable liquid first component, and (ii) a secondsolidifiable component that is different from said first component, saidmethod further comprising: concurrently with or following the forming ofsaid three dimensional object, solidifying and/or curing said secondsolidifiable component in said three-dimensional object.
 20. The methodof claim 19, wherein said second component comprises a polymerizableliquid solubilized in or suspended in said first component.
 21. Themethod of claim 19, wherein said second component comprises: (i) apolymerizable solid suspended in said first component; (ii) apolymerizable solid solubilized in said first component; or (iii) apolymer solubilized in said first component.
 22. The method of claim 19,wherein said three-dimensional intermediate is collapsible orcompressible.
 23. The method of claim 19, wherein said three-dimensionalobject comprises a polymer blend, interpenetrating polymer network,semi-interpenetrating polymer network, or sequential interpenetratingpolymer network formed from said first component and said secondcomponent.
 24. The method of claim 19, wherein said polymerizable liquidcomprises: from 1 or 10 percent by weight to 40, 90 or 99 percent byweight of said first component; and from 1, 10 or 60 percent by weightto 90 or 99 percent by weight of said second component.
 25. The methodof claim 19, wherein said solidifying and/or curing step (d) is carriedout concurrently with said irradiating step (c) and: (i) saidsolidifying and/or curing step is carried out by precipitation; or (ii)said irradiating step generates heat from the polymerization of saidfirst component in an amount sufficient to thermally solidify orpolymerize said second component.
 26. The method of claim 19, whereinsaid solidifying and/or curing step (d) is carried out subsequent tosaid irradiating step (c) and is carried out by: (i) heating said secondsolidifiable component; (ii) irradiating said second solidifiablecomponent with light at a wavelength different from that of the light insaid irradiating step (c); (iii) contacting said second polymerizablecomponent to water; and/or (iv) contacting said second polymerizablecomponent to a catalyst.
 27. The method of claim 19, wherein: saidsecond component comprises the precursors to a polyurethane, polyurea,or copolymer thereof, a silicone resin, an epoxy resin, a cyanate esterresin, or a natural rubber; and said solidifying step is carried out byheating and/or microwave irradiating.
 28. The method of claim 19,wherein: said second component comprises the precursors to apolyurethane, polyurea, or copolymer thereof, and said solidifyingand/or curing step is carried out by contacting said second component towater.
 29. The method of claim 19, wherein: said solidifying and/orcuring step (d) is carried out subsequent to said irradiating step; andsaid solidifying and/or curing step (d) is carried out under conditionsin which said solid polymer scaffold degrades and forms a constituentnecessary for the polymerization of said second component.
 30. Themethod of claim 19, wherein: said second component comprises precursorsto a polyurethane, polyurea, or copolymer thereof, a silicone resin, aring-opening metathesis polymerization resin, or a click chemistryresin, a cyanate ester resin, and said solidifying and/or curing step iscarried out by contacting said second component to a polymerizationcatalyst.
 31. The method of claim 19, wherein said polymerizable liquidcomprises a first component and at least one additional component, saidfirst component comprising monomers and/or prepolymers that can bepolymerized by exposure to actinic radiation or light; said secondcomponent solidifiable on contacting to heat, water, water vapor, lightat a different wavelength than that at which said first component ispolymerized, catalysts, evaporation of a solvent from the polymerizableliquid, exposure to microwave irradiation, and combinations thereof. 32.The method of claim 31, said first component monomers and/or prepolymerscomprising reactive end groups selected from the group consisting ofacrylates, methacrylates, α-olefins, N-vinyls, acrylamides,methacrylamides, styrenics, epoxides, thiols, 1,3-dienes, vinyl halides,acrylonitriles, vinyl esters, maleimides, and vinyl ethers.
 33. Themethod of claim 31, said additional component comprising monomers and/orprepolymers comprising reactive end groups selected from the groupconsisting of: epoxy/amine, epoxy/hydroxyl, oxetane/amine,oxetane/alcohol, isocyanate/hydroxyl, isocyanate/amine,isocyanate/carboxylic acid, cyanate ester, anhydride/amine,amine/carboxylic acid, amine/ester, hydroxyl/carboxylic acid,hydroxyl/acid chloride, amine/acid chloride, vinyl/Si—H, Si—Cl/hydroxyl,Si—Cl/amine, hydroxyl/aldehyde, amine/aldehyde, hydroxymethyl oralkoxymethyl amide/alcohol, aminoplast, alkyne/azide, click chemistryreactive groups, alkene/sulfur, alkene/thiol, alkyne/thiol,hydroxyl/halide, isocyanate/water, Si—OH/hydroxyl, Si—OH/water,Si—OH/Si—H, Si—OH/Si—OH, perfluorovinyl, diene/dienophiles, olefinmetathesis polymerization groups, olefin polymerization groups forZiegler-Natta catalysis, and ring-opening polymerization groups andmixtures thereof.
 34. The method of claim 19, wherein saidthree-dimensional object comprises an interpenetrating polymer network(IPN), said interpenetrating polymer network comprising a sol-gelcomposition, a hydrophobic-hydrophilic IPN, a phenolic resin, apolyimide, a conductive polymer, a natural product-based IPN, asequential IPN, a polyolefin, or a combination thereof.